Circumferential ablation device assembly and methods of use and manufacture providing an ablative circumferential band along an expandable member

ABSTRACT

A medical balloon catheter assembly includes a balloon having a permeable region and a non-permeable region. The balloon is constructed at least in part from a fluid permeable tube such that the permeable region is formed from a porous material which allows a volume of pressurized fluid to pass from within a chamber formed by the balloon and into the permeable region sufficiently such that the fluid may be ablatively coupled to tissue engaged by the permeable region. The non-permeable region is adapted to substantially block the pressurized fluid from passing from within the chamber and outwardly from the balloon. The porous material may be a porous fluoropolymer, such as porous polytetrafluoroethylene, and the pores may be created by voids that are inherently formed between an interlocking node-fibril network that makes up the fluoropolymer. Such voids may be created according to one mode by expanding the fluoropolymer. The balloon may be formed such that the porous material extends along both the permeable and non-permeable regions. In one mode of this construction, the porous material is porous along the permeable region but is non-porous along the non-permeable region, such as for example by expanding only the permeable region in order to render sufficient voids in the node-fibril network to provide permeable pores in that section. The voids or pores in the porous material may also be provided along both permeable and non-permeable sections but are substantially blocked with an insulator material along the non-permeable section in order to prevent fluid from passing therethrough. The insulator material may be dip coated, deposited, or extruded with the porous material in order to fill the voids. The insulator material may in one mode be provided along the entire working length of the balloon and then selectively removed along the permeable section, or may be selectively exposed to only the non-permeable sections in order to fill the voids or pores there.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 60/125,928, filed Mar. 23, 1999 and U.S. Provisional ApplicationSer. No. 60/125,509, filed Mar. 19, 1999; and is also a divisionalapplication of U.S. patent application Ser. No. 09/435,283, filed Nov.5, 1999, now U.S. Pat. No. 6,500,174, which is a continuation-in-part ofU.S. patent application Ser. No. 08/889,798, filed Jul. 8, 1997, nowU.S. Pat. No. 6,024,740.

FIELD OF THE INVENTION

The present invention involves a surgical device and methods ofmanufacture and use. More specifically, it involves a circumferentialablation device assembly and associated methods of manufacture and use.One aspect of the present invention specifically involves an assemblyand method incorporating a circumferential band along an intermediateregion of an expandable member's working length for ablating acircumferential region of tissue engaged to the intermediate region at alocation where a pulmonary vein extends from a left atrium.

BACKGROUND

The terms “body space,” including derivatives thereof, is hereinintended to mean any cavity or lumen within the body which is defined atleast in part by a tissue wall. For example, the cardiac chambers, theuterus, the regions of the gastrointestinal tract, and the arterial orvenous vessels are all considered illustrative examples of body spaceswithin the intended meaning.

The term “body lumen,” including derivatives thereof, is herein intendedto mean any body space which is circumscribed along a length by atubular tissue wall and which terminates at each of two ends in at leastone opening that communicates externally of the body space. For example,the large and small intestines, the vas deferens, the trachea, and thefallopian tubes are all illustrative examples of lumens within theintended meaning. Blood vessels are also herein considered lumens,including regions of the vascular tree between their branch points. Moreparticularly, the pulmonary veins are lumens within the intendedmeaning, including the region of the pulmonary veins between thebranched portions of their ostia along a left ventricle wall, althoughthe wall tissue defining the ostia typically presents uniquely taperedlumenal shapes.

Many local energy delivery devices and methods have been developed fortreating the various abnormal tissue conditions in the body, andparticularly for treating abnormal tissue along body space walls whichdefine various body spaces in the body. For example, various deviceshave been disclosed with the primary purpose of treating or recanalizingatherosclerotic vessels with localized energy delivery. Several priordevices and methods combine energy delivery assemblies in combinationwith cardiovascular stent devices in order to locally deliver energy totissue in order to maintain patency in diseased lumens such as bloodvessels. Endometriosis, another abnormal wall tissue condition which isassociated with the endometrial cavity and is characterized bydangerously proliferative uterine wall tissue along the surface of theendometrial cavity, has also been treated by local energy deliverydevices and methods. Several other devices and methods have also beendisclosed which use catheter-based heat sources for the intended purposeof inducing thrombosis and controlling hemorrhaging within certain bodylumens such as vessels. Detailed examples of local energy deliverydevices and related procedures such as those of the types just describedabove are variously disclosed in the following references: U.S. Pat.Nos. 4,672,962 to Hershenson; U.S. Pat. Nos. 4,676,258 to InoKuchi etal.; U.S. Pat. No. 4,790,311 to Ruiz; U.S. Pat. No. 4,807,620 to Strulet al.; U.S. Pat. No. 4,998,933 to Eggers et al.; U.S. Pat. No.5,035,694 to Kasprzyk et al.; U.S. Pat. No. 5,190,540 to Lee; U.S. Pat.No. 5,226,430 to Spears et al.; and U.S. Pat. No. 5,292,321 to Lee; U.S.Pat. No. 5,449,380 to Chin; U.S. Pat. No. 5,505,730 to Edwards; U.S.Pat. No. 5,558,672 to Edwards et al.; and U.S. Pat. No. 5,562,720 toStern et al. ; U.S. Pat. No. 4,449,528 to Auth et al.; U.S. Pat. No.4,522,205 to Taylor et al.; and U.S. Pat. No. 4,662,368 to Hussein etal.; U.S. Pat. No. 5,078,736 to Behl; and U.S. Pat. No. 5,178,618 toKandarpa. The disclosures of these references are herein incorporated intheir entirety by reference thereto.

Other prior devices and methods electrically couple fluid to an ablationelement during local energy delivery for treatment of abnormal tissues.Some such devices couple the fluid to the ablation element for theprimary purpose of controlling the temperature of the element during theenergy delivery. Other such devices couple the fluid more directly tothe tissue-device interface either as another temperature controlmechanism or in certain other known applications as a carrier or mediumfor the localized energy delivery, itself. More detailed examples ofablation devices which use fluid to assist in electrically couplingelectrodes to tissue are disclosed in the following references: U.S.Pat. No. 5,348,554 to Imran et al.; U.S. Pat. No. 5,423,811 to Imran etal.; U.S. Pat. No. 5,505,730 to Edwards; U.S. Pat. No. 5,545,161 toImran et al.; U.S. Pat. No. 5,558,672 to Edwards et al.; U.S. Pat. No.5,569,241 to Edwards; U.S. Pat. No. 5,575,788 to Baker et al.; U.S. Pat.No. 5,658,278 to Imran et al.; U.S. Pat. No. 5,688,267 to Panescu etal.; U.S. Pat. No. 5,697,927 to Imran et al.; U.S. Pat. No. 5,722,403 toMcGee et al.; U.S. Pat. No. 5,769,846; and PCT Patent ApplicationPublication No. WO 97/32525 to Pomeranz et al.; and PCT PatentApplication Publication No. WO 98/02201 to Pomeranz et al. To the extentnot previously incorporated above, the disclosures of these referencesare herein incorporated in their entirety by reference thereto.

Atrial Fibrillation

Cardiac arrhythmias, and atrial fibrillation in particular, persist ascommon and dangerous medical ailments associated with abnormal cardiacchamber wall tissue, and has been observed especially in the agingpopulation. In patients with cardiac arrhythmia, abnormal regions ofcardiac tissue do not follow the synchronous beating cycle associatedwith normally conductive tissue in patients with sinus rhythm. Instead,the abnormal regions of cardiac tissue aberrantly conduct to adjacenttissue, thereby disrupting the cardiac cycle into an asynchronouscardiac rhythm. Such abnormal conduction has been previously known tooccur at various regions of the heart, such as, for example, in theregion of the sino-atrial (SA) node, along the conduction pathways ofthe atrioventricular (AV) node and the Bundle of His, or in the cardiacmuscle tissue forming the walls of the ventricular and atrial cardiacchambers.

Cardiac arrhythmias, including atrial arrhythmia, may be of amultiwavelet reentrant type, characterized by multiple asynchronousloops of electrical impulses that are scattered about the atrial chamberand are often self-propagating. In the alternative or in addition to themultiwavelet reentrant type, cardiac arrhythmias may also have a focalorigin, such as when an isolated region of tissue in an atrium firesautonomously in a rapid, repetitive fashion. Cardiac arrhythmias,including atrial fibrillation, may be generally detected using theglobal technique of an electrocardiogram (EKG). More sensitiveprocedures of mapping the specific conduction along the cardiac chambershave also been disclosed, such as, for example, in U.S. Pat. Nos.4,641,649 to Walinsky et al. and Published PCT Patent Application No. WO96/32897 to Desai. The disclosures of these references are hereinincorporated in their entirety by reference thereto.

A host of clinical conditions may result from the irregular cardiacfunction and resulting hemodynamic abnormalities associated with atrialfibrillation, including stroke, heart failure, and other thromboembolicevents. In fact, atrial fibrillation is believed to be a significantcause of cerebral stroke, wherein the abnormal hemodynamics in the leftatrium caused by the fibrillatory wall motion precipitate the formationof thrombus within the atrial chamber. A thromboembolism is ultimatelydislodged into the left ventricle, which thereafter pumps the embolisminto the cerebral circulation where a stroke results. Accordingly,numerous procedures for treating atrial arrhythmias have been developed,including pharmacological, surgical, and catheter ablation procedures

Several pharmacological approaches intended to remedy or otherwise treatatrial arrhythmias have been disclosed, such as for example according tothe disclosures of the following references: U.S. Pat. No. 4,673,563 toBerne et al.; U.S. Pat. No. 4,569,801 to Molloy et al.; and also“Current Management of Arrhythmias” (1991) by Hindricks, et al. However,such pharmacological solutions are not generally believed to be entirelyeffective in many cases, and are even believed in some cases to resultin proarrhythmia and long-term inefficacy. The disclosures of thesereferences are herein incorporated in their entirety by referencethereto.

Several surgical approaches have also been developed with the intentionof treating atrial fibrillation. One particular example is known as the“maze procedure,” as is disclosed by Cox, J L et al. in “The surgicaltreatment of atrial fibrillation. I. Summary” Thoracic andCardiovascular Surgery 101(3), pp. 402-405 (1991); and also by Cox, J Lin “The surgical treatment of atrial fibrillation. IV. SurgicalTechnique”, Thoracic and Cardiovascular Surgery 101(4), pp. 584-592(1991). In general, the “maze” procedure is designed to relieve atrialarrhythmia by restoring effective atrial systole and sinus node controlthrough a prescribed pattern of incisions about the tissue wall. In theearly clinical experiences reported, the “maze” procedure includedsurgical incisions in both the right and the left atrial chambers.However, more recent reports predict that the surgical “maze” proceduremay be substantially efficacious when performed only in the left atrium,such as is disclosed in Sueda et al., “Simple Left Atrial Procedure forChronic Atrial Fibrillation Associated With Mitral Valve Disease”(1996). The disclosures of these cited references are hereinincorporated in their entirety by reference thereto.

The “maze procedure” as performed in the left atrium generally includesforming vertical incisions from the two superior pulmonary veins andterminating in the region of the mitral valve annulus, traversing theregion of the inferior pulmonary veins en route. An additionalhorizontal line also connects the superior ends of the two verticalincisions. Thus, the atrial wall region bordered by the pulmonary veinostia is isolated from the other atrial tissue. In this process, themechanical sectioning of atrial tissue eliminates the arrhythmogenicconduction from the boxed region of the pulmonary veins and to the restof the atrium by creating conduction blocks within the aberrantelectrical conduction pathways. Other variations or modifications ofthis specific pattern just described have also been disclosed, allsharing the primary purpose of isolating known or suspected regions ofarrhythmogenic origin or propagation along the atrial wall.

While the “maze” procedure and its variations as reported by Cox andothers have met some success in treating patients with atrialarrhythmia, its highly invasive methodology is believed to beprohibitive in most cases. However, these procedures have provided aguiding principle that electrically isolating faulty cardiac tissue maysuccessfully prevent atrial arrhythmia, and particularly atrialfibrillation caused by arrhythmogenic conduction arising from the regionof the pulmonary veins.

Less invasive catheter-based approaches to treat atrial fibrillationhave been disclosed which implement cardiac tissue ablation forterminating arrhythmogenic conduction in the atria. Examples of suchcatheter-based devices and treatment methods have generally targetedatrial segmentation with ablation catheter devices and methods adaptedto form linear or curvilinear lesions in the wall tissue that definesthe atrial chambers. Some specifically disclosed approaches providespecific ablation elements that are linear over a defined lengthintended to engage the tissue for creating the linear lesion. Otherdisclosed approaches provide shaped or steerable guiding sheaths, orsheaths within sheaths, for the intended purpose of directing tipablation catheters toward the posterior left atrial wall such thatsequential ablations along the predetermined path of tissue may createthe desired lesion. In addition, various energy delivery modalities havebeen disclosed for forming atrial wall lesions, and include use ofmicrowave, laser, ultrasound, thermal conduction, and more commonly,radiofrequency energies to create conduction blocks along the cardiactissue wall.

Further more detailed examples of ablation device assemblies and methodsfor creating lesions along an atrial wall are disclosed in the followingU.S. Patent references: U.S. Pat. No. 4,898,591 to Jang et al.; U.S.Pat. No. 5,104,393 to Isner et al.; U.S. Pat. No. 5,427,119; U.S. Pat.No. 5,487,385 to Avitall; U.S. Pat. No. 5,497,119 to Swartz et al.; U.S.Pat. No. 5,545,193 to Fleischman et al.; U.S. Pat. No. 5,549,661 toKordis et al.; U.S. Pat. No. 5,575,810 to Swanson et al.; U.S. Pat. No.5,564,440 to Swartz et al.; U.S. Pat. No. 5,592,609 to Swanson et al.;U.S. Pat. No. 5,575,766 to Swartz et al.; U.S. Pat. No. 5,582,609 toSwanson; U.S. Pat. No. 5,617,854 to Munsif; U.S. Pat. No. 5,687,723 toAvitall; U.S. Pat. No. 5,702,438 to Avitall. To the extent notpreviously incorporated above, the disclosures of these references areherein incorporated in their entirety by reference thereto.

Other examples of such ablation devices and methods are disclosed in thefollowing Published PCT Patent Applications: WO 93/20767 to Stern etal.; WO 94/21165 to Kordis et al.; WO 96/10961 to Fleischman et al.; WO96/26675 to Klein et al.; and WO 97/37607 to Schaer. To the extent notpreviously incorporated above, the disclosures of these references areherein incorporated in their entirety by reference thereto.

Additional examples of such ablation devices and methods are disclosedin the following published articles: “Physics and Engineering ofTranscatheter Tissue Ablation”, Avitall et al., Journal of AmericanCollege of Cardiology, Volume 22, No. 3:921-932 (1993); and “Right andLeft Atrial Radiofrequency Catheter Therapy of Paroxysmal AtrialFibrillation,” Haissaguerre, et al., Journal of CardiovascularElectrophysiology 7(12), pp. 1132-1144 (1996). The disclosures of thesereferences are herein incorporated in their entirety by referencethereto.

In addition to those known assemblies just summarized above, additionaltissue ablation device assemblies have also been recently developed forthe specific purpose of ensuring firm contact and consistent positioningof a linear ablation element along a length of tissue by anchoring theelement at least at one predetermined location along that length, suchas in order to form a “maze”-type lesion pattern in the left atrium. Oneexample of such assemblies includes an anchor at each of two ends of alinear ablation element in order to secure those ends to each of twopredetermined locations along a left atrial wall, such as at twoadjacent pulmonary veins, so that tissue may be ablated along the lengthof tissue extending therebetween.

In addition to attempting atrial wall segmentation with long linearlesions for treating atrial arrhythmia, other ablation device and methodhave also been disclosed which are intended to use expandable memberssuch as balloons to ablate cardiac tissue. Some such devices have beendisclosed primarily for use in ablating tissue wall regions along thecardiac chambers. Other devices and methods have been disclosed fortreating abnormal conduction of the left-sided accessory pathways, andin particular associated with “Wolff-Parkinson-White” syndrome—varioussuch disclosures use a balloon for ablating from within a region of anassociated coronary sinus adjacent to the desired cardiac tissue toablate. Further more detailed examples of devices and methods such as ofthe types just described are variously disclosed in the followingpublished references: Fram et al., in “Feasibility of RF Powered ThermalBalloon Ablation of Atrioventricular Bypass Tracts via the CoronarySinus: In vivo Canine Studies,” PACE, Vol. 18, p 1518-1530 (1995);“Long-term effects of percutaneous laser balloon ablation from thecanine coronary sinus”, Schuger C D et al., Circulation (1992)86:947-954; and “Percutaneous laser balloon coagulation of accessorypathways”, McMath L P et al., Diagn Ther Cardiovasc Interven 1991;1425:165-171. The disclosures of these references are hereinincorporated in their entirety by reference thereto.

Arrhythmias Originating from Foci in Pulmonary Veins

Various modes of atrial fibrillation have also been observed to be focalin nature, caused by the rapid and repetitive firing of an isolatedcenter within cardiac muscle tissue associated with the atrium. Suchfoci may act as either a trigger of atrial fibrillatory paroxysmal ormay even sustain the fibrillation. Various disclosures have suggestedthat focal atrial arrhythmia often originates from at least one tissueregion along one or more of the pulmonary veins of the left atrium, andeven more particularly in the superior pulmonary veins.

Less-invasive percutaneous catheter ablation techniques have beendisclosed which use end-electrode catheter designs with the intention ofablating and thereby treating focal arrhythmias in the pulmonary veins.These ablation procedures are typically characterized by the incrementalapplication of electrical energy to the tissue to form focal lesionsdesigned to terminate the inappropriate arrhythmogenic conduction.

One example of a focal ablation method intended to treat focalarrhythmia originating from a pulmonary vein is disclosed byHaissaguerre, et al. in “Right and Left Atrial Radiofrequency CatheterTherapy of Paroxysmal Atrial Fibrillation” in Journal of CardiovascularElectrophysiology 7(12), pp. 1132-1144 (1996) (previously incorporatedby reference above). Haissaguerre, et al. discloses radiofrequencycatheter ablation of drug-refractory paroxysmal atrial fibrillationusing linear atrial lesions complemented by focal ablation targeted atarrhythmogenic foci in a screened patient population. The site of thearrhythmogenic foci were generally located just inside the superiorpulmonary vein, and the focal ablations were generally performed using astandard 4 mm tip single ablation electrode.

Another focal ablation method of treating atrial arrhythmias isdisclosed in Jais et al., “A focal source of atrial fibrillation treatedby discrete radiofrequency ablation,” Circulation 95:572-576 (1997). Thedisclosure of this reference is herein incorporated in its entirety byreference thereto. Jais et al. discloses treating patients withparoxysmal arrhythmias originating from a focal source by ablating thatsource. At the site of arrhythmogenic tissue, in both right and leftatria, several pulses of a discrete source of radiofrequency energy wereapplied in order to eliminate the fibrillatory process.

Other assemblies and methods have been disclosed addressing focalsources of arrhythmia in pulmonary veins by ablating circumferentialregions of tissue either along the pulmonary vein, at the ostium of thevein along the atrial wall, or encircling the ostium and along theatrial wall. More detailed examples of device assemblies and methods fortreating focal arrhythmia as just described are disclosed in PublishedPCT Patent Application No. WO 99/02096 to Diederich et al., and also inthe following pending U.S. Patent Applications: U.S. Ser. No. 08/889,798for “Circumferential Ablation Device Assembly” to Michael D. Lesh etal., filed Jul. 8, 1997; U.S. Ser. No. 08/889,835 for “Device and Methodfor Forming a Circumferential Conduction Block in a Pulmonary Vein” toMichael D. Lesh, filed Jul. 8, 1997; U.S. Ser. No. 09/199,736 for“Circumferential Ablation Device Assembly” to Chris J. Diederich et al.,filed Feb. 3, 1998; and U.S. Ser. No. 09/260,316 for “Device and Methodfor Forming a Circumferential Conduction Block in a Pulmonary Vein” toMichael D. Lesh.

Another specific device assembly and method which is intended to treatfocal atrial fibrillation by ablating a circumferential region of tissuebetween two seals in order to form a conduction block to isolate anarrhythmogenic focus within a pulmonary vein is disclosed in U.S. Pat.No. 5,938,660 and a related Published PCT Patent Application No. WO99/00064. The disclosures of these references are herein incorporated intheir entirety by reference thereto.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a circumferential ablationdevice assembly, and related method of manufacture and use, whichablates a circumferential region of tissue at a location where apulmonary vein extends from an atrium by ablatively coupling an ablativefluid medium within an expandable member to the circumferential regionof tissue across a circumferential band which circumscribes anintermediate region of the expandable member and engages thecircumferential region of tissue when the expandable member is expanded.

It is another object of the invention to provide such a circumferentialablation device assembly, and related methods of use and manufacture,wherein the intermediate region of the expandable member's workinglength is constructed at least in part of a porous fluoropolymermaterial.

It is a further object of the invention to provide such an expandablemember with the porous fluoropolymer material along the intermediateregion and also with first and second end portions of the working lengththat do not include a fluoropolymer.

It is another object of the invention to provide a circumferentialablation device assembly, and related methods of manufacture and use,which ablatively couples an ablation element to only a region of tissueengaged to an intermediate region between two end portions along aworking length of an expandable member.

It is another object of the invention to provide a medical deviceassembly which ablatively couples an ablative fluid medium from withinan expandable member to only a region of tissue engaged to only a fluidpermeable section along the working length of the expandable member.

It is a further object of the invention to provide a circumferentialablation device assembly, and related methods of use and manufacture,that includes a balloon with elastomeric first and second end portionsalong its working length and also with a fluid permeable circumferentialband circumscribing an intermediate region between those end portions.

It is a further object of the invention to provide a circumferentialablation device assembly, and related methods of use and manufacture,that includes a balloon having a fluid permeable fluoropolymer that isintegral along the balloon's working length and includes an insulator oneach of two end portions of the working length such that only acircumferential band circumscribing an intermediate region between theend portions is left permeable. It is a further object to provide such aballoon with the two end portions impregnated with a filler as fluidinsulation.

It is a further object of the invention to provide a circumferentialablation device assembly, and related methods of use and manufacture,that includes an expandable member having a working length constructedof an elastomeric wall that is constructed to be fluid permeable alongonly a circumferential band which circumscribes an intermediate regionlocated between two end portions of the working length.

It is a further object of the invention to provide a circumferentialablation device assembly, and related methods of use and manufacture,that includes a balloon with a fluoropolymeric material that is integralalong the balloon's working length while only an intermediate regionbetween two end portions of the working length is fluid permeable toallow for ablative coupling of an ablation medium across thefluoropolymeric material.

It is a further object of the invention to provide a circumferentialablation device assembly, and related methods of use and manufacture,that includes a balloon having a working length with relatively elasticfirst and second end portions and a relatively inelastic intermediateregion between the first and second end portions, and which ablates onlya circumferential region of tissue surrounding the intermediate regionwhen the balloon is inflated.

It is a further object of the invention to provide a medical devicecatheter having a balloon with a working length that has a porousfluoropolymeric permeable section and also an elastomeric section.

It is a further object of the invention to provide such a catheter wherethe permeable fluoropolymer section is between two elastomeric endportions of the working length.

It is a further object of the invention to provide a circumferentialablation member with an expandable member having a taper along theworking length and also with an ablation element coupled to acircumferential area surrounding the taper along the working length.

It is also a further object of the invention to provide acircumferential ablation member which an expandable member that isadapted to seat at a pulmonary vein ostium such that an ablationcircumferential band surrounding the working length is aligned with andablates a region of tissue along the ostium.

It is a further object of the invention to provide a circumferentialablation member for ablating a circumferential region of tissue along apulmonary vein ostium and which includes an expandable member with aworking length having two end portions that have larger outer diametersthan an intermediate region of the working length that includes anablative circumferential band which is adapted to seat at the pulmonaryvein ostium.

Other objects of the invention are contemplated which would be apparentto one of ordinary skill based upon the totality of this disclosure,including without limitation the following summary of various modes,aspects, features, and variations of the particular embodiments.

In one mode of the invention, a circumferential ablation device assemblyincludes an elongate body with a circumferential ablation member alongits distal end portion having an expandable member. The expandablemember is located along the distal end portion of the elongate body, andis expandable along a working length which encloses at least in part afluid chamber that is adapted to fluidly couple to a pressurizeablesource of fluid. The working length also has first and second endportions and an intermediate region extending between the end portions.The end portions are substantially non-permeable to fluid, whereas theintermediate region is fluid permeable. With the working length expandedto a radially expanded condition, the intermediate region has anexpanded outer diameter that is adapted to radially engage thecircumferential region of tissue. The working length is thus adapted toallow fluid to pass from within the fluid chamber and outwardly into thepermeable section of the intermediate region where it may be ablativelycoupled to the engaged circumferential region of tissue.

In one aspect of this mode, the circumferential ablation member includesan ablation electrode element that is constructed to electrically coupleto a volume of pressurized electrically conductive fluid passing fromwithin the fluid chamber and into the permeable section of theintermediate region of the working length. Accordingly, current from theelectrode element flows through the electrically conductive fluid andoutwardly from the ablation member only through the permeable sectionalong the intermediate region and into the circumferential region oftissue for ablation there.

In another aspect of this mode, the permeable section is constructedfrom a substantially non-permeable material that has a plurality ofapertures formed therethrough which form pores to render that sectionpermeable, whereas in another aspect the permeable section is insteadconstructed from an inherently porous material with the permeabilityarising from a plurality of pores that are integral to the porousmaterial.

In another aspect of this mode, the permeable section comprises a porousfluoropolymer material, and may be more particularly a porouspolytetrafluoroethylene material.

In another aspect of this mode, the expandable member is an inflatableballoon. The balloon is inflatable with pressurized fluid in order toexpand from the radially collapsed condition to the radially expandedcondition.

In one particular beneficial construction, the balloon along theintermediate region is constructed at least in part from a porousfluoropolymer material which forms the permeable section, and along thefirst and second end portions the balloon is constructed at least inpart from an elastomer.

In another aspect of this mode, the permeable section forms acircumferential band that circumscribes the working length along theintermediate region. In one particular variation of this aspect, thecircumferential band has a band length relative to the longitudinal axisand which is substantially shorter than the working length, and may beless than two-thirds the working length or even one-half of the workinglength.

In another aspect of this mode, the working length has a proximal endand a distal end and also has a tapered shape with a distally reducingouter diameter from the proximal end to the distal end. In one moreparticular beneficial variation, the tapered shape is “pear”-shaped andhas a contoured surface between the proximal end and the distal end witha relatively “forward” or “distal”-looking face along the contouredsurface adjacent the proximal end. Further to this variation, thepermeable section is provided along a distally-looking face and isadapted to be advanced distally against a circumferential region oftissue when expanded, such as in order to ablate a region of tissuealong a posterior left atrial wall which surrounds a pulmonary veinostium and isolates the associated vein from a substantial portion ofthe left atrium.

Another mode of the invention provides a medical catheter assembly witha balloon positioned along a distal end portion of an elongate bodywhich ablatively couples an ablation element to tissue via an ablativemedium provided by a fluid along a fluid permeable portion of theballoon. The balloon defines a fluid chamber and has a working lengththat is expandable with a volume of pressurized fluid from a radiallycollapsed condition having a radially collapsed profile to a radiallyexpanded condition having a radially expanded profile which is largerthan the radially collapsed profile. The working length further includesa non-permeable section and a permeable section. The non-permeablesection is constructed to substantially prevent the pressurized fluidfrom passing from within the fluid chamber and outwardly through andfrom the balloon in the radially expanded condition. The permeablesection is constructed at least in part of a porous material having aplurality of pores. In the radially expanded condition the pores areconstructed to substantially allow the pressurized fluid to pass fromwithin the enclosed chamber and outwardly from the balloon through thepermeable section.

In one aspect of this mode, the porous material is constructed at leastin part from a porous fluoropolymer material and the plurality of poresare integrally formed in the porous fluoropolymer material.

In one beneficial variation of this aspect, the porous fluoropolymermaterial includes a porous polytetrafluoroethylene material. The poresaccording to this variation may be formed by and between a plurality ofnodes which are interconnected by a plurality of fibrils that make upthe polytetrafluoroethylene material, and may be located along a lengthof the porous polytetrafluoroethylene material which extends along boththe non-permeable and permeable sections.

According to the polytetrafluoroethylene embodiment providing the poresalong both the permeable and non-permeable sections, the pores along thenon-permeable section are substantially blocked and non-permeable to thepressurized fluid within the fluid chamber and the pores along thepermeable section are substantially open and permeable to pressurizedfluid within the fluid chamber. Further to this embodiment, the poresalong the non-permeable section may be blocked with an insulatormaterial, which may be a polymer, or more specifically an elastomer inorder to provide the working length of the balloon elastomeric qualitiesduring in vivo use. In further embodiments, the insulator material maybe a deposited material, such as plasma deposited materials, vapordeposited materials, ion beam deposited materials, or sputter coatedmaterials, or may be a dip-coated material, or may be a thermoplasticmaterial which is melted to the porous polytetrafluoroethylene materialalong the non-permeable section. In still further embodiments, theinsulator material may be a coating over the outer surface of the porouspolytetrafluoroethylene, such as a tubular material that may be anelastomer which is coaxially disposed relative to the non-permeablesection, or may be a filler material within the pores along thenon-permeable section.

In one specific beneficial variation, the porous polytetrafluoroethylenematerial is formed in a porous tube which is relatively non-compliant,and the tubular material further comprises an elastomer which isrelatively compliant, such that the balloon in the radially collapsedcondition is characterized by the porous polytetrafluoroethylenematerial in a folded condition and also by the tubular material in arelatively non-stretched condition, and the balloon in the radiallyexpanded condition is characterized by the porouspolytetrafluoroethylene material in an unfolded condition and also bythe tubular material in a radially stretched condition.

In another variation of the porous polytetrafluoroethylene aspect, theporous material is formed from a tape which is oriented in a helicalpattern with adjacent windings which are fused to form a continuousporous tube that defines at least in part the fluid chamber.

In another aspect of this mode, the working length is constructed atleast in part from a polytetrafluoroethylene material having a lengththat extends along both the non-permeable and permeable sections. Thepolytetrafluoroethylene material according to this aspect issubstantially non-porous along the non-permeable section, and is porousalong the permeable section to thereby form the porous material.

In one variation of this aspect, the polytetrafluoroethylene materialalong the non-permeable section includes a plurality of non-permeablepores. The non-permeable pores are sufficiently small to prevent passageof the pressurized fluid from within the fluid chamber and outwardlyfrom the balloon through the non-permeable section, and thepolytetrafluoroethylene material along that section is thereforeeffectively non-porous. In a further more detailed embodiment of thisvariation, the plurality of pores along the permeable section are formedby and between a first plurality of nodes which are interconnected by afirst plurality of fibrils, whereas the plurality of non-permeable poresare formed by and between a second plurality of nodes andinterconnecting fibrils.

In another variation of the polytetrafluoroethylene material aspect, thematerial is expanded from a cured state along the permeable section andis relatively un-expanded and substantially in the cured state along thenon-permeable section, such as for example being stretched andunstretched in the permeable and non-permeable sections, respectively.

In another aspect of this mode, the working length includes first andsecond end portions with an intermediate region extending therebetween.The first end portion includes the non-permeable section, theintermediate region includes the permeable section, and the second endportion includes a second non-permeable section of similar constructionto the first non-permeable section.

In one beneficial variation of this aspect, the permeable section formsa circumferential band that circumscribes the working length along theintermediate region. In the radially expanded condition the intermediateregion is constructed to radially engage a circumferential region oftissue along a body space wall of a body space, whereas the first andsecond end portions are further constructed to radially engage first andsecond adjacent regions of tissue, respectively, on opposite sides ofthe circumferential region of tissue. The permeable section is adaptedto allow a volume of electrically conductive fluid to pass from withinthe fluid chamber and outwardly from the balloon through the pores. Theassembly according to this beneficial variation further includes anablation electrode that is constructed to electrically couple with theelectrically conductive fluid within the fluid chamber and therefore tothe circumferential region of tissue as the electrically conductivefluid flows outwardly from the balloon through the permeable section.According to this beneficial assembly, the electrical coupling from theablation electrode and through the volume of electrically conductivefluid passing through the permeable section is substantially isolated tothe circumferential region of tissue engaged by the intermediate regionand is substantially shielded from the adjacent regions of tissue by thefirst and second end portions.

In another aspect of this mode, the non-permeable and permeable sectionsare located longitudinally adjacent each other along the working lengthrelative to the longitudinal axis, and in one particular variation thepermeable section is located distally adjacent the non-permeablesection.

In another aspect of this mode, the working length has a proximalsection and a distal section and a tapered shape with a distallyreducing outer diameter from the proximal section to the distal section,and the permeable section is located along the tapered region. In oneparticular variation of this aspect, the permeable section forms acircumferential band that circumscribes the working length along thetaper.

In another aspect of this mode, the permeable section is furtherconstructed to allow a volume of electrically conductive fluid to passfrom within the fluid chamber and outwardly through and from the balloonthrough the pores, and the assembly further includes an ablationelectrode which is constructed to electrically couple to the volume ofelectrically conductive fluid within the fluid chamber.

Another mode of the invention is a method for forming a medical ballooncatheter device assembly that is adapted to deliver a volume of fluid toa region of tissue in a body. This method includes constructing a fluidpermeable tube having a permeable section formed at least in part from aporous material. This construction uses a porous material having aplurality of pores which are adapted to allow a volume of pressurizedfluid to pass from within and outwardly through the tube, and furtherresults in a tubular construction having a non-permeable section whichis adapted to substantially prevent the volume of pressurized fluid frompassing from within and outwardly through the tube. This method furtherincludes securing the fluid permeable tube to a distal end portion of anelongate catheter body in order to form a balloon which defines apressurizeable fluid chamber over the catheter body and which includes aworking length that is adapted to radially expand from a radiallycollapsed condition to a radially expanded condition when the fluidchamber is filled with the pressurized fluid. The method also includescoupling the pressurizeable fluid chamber with a distal port of a fluidpassageway that extends along the catheter body between the distal portand a proximal port along the proximal end portion of the elongatecatheter body which is adapted to couple to a pressurizeable fluidsource, and also includes positioning the permeable section along theworking length.

One aspect of this method mode further includes forming a taper alongthe working length of the balloon having a distally reducing outerdiameter, and positioning the permeable section along the taper. Thenon-permeable section may also be positioned along the taper.

Another aspect of this method includes constructing the fluid permeabletube at least in part from a porous fluoropolymer having a plurality ofvoids that form the pores.

One variation of this aspect also includes constructing the porousfluoropolymer to include a plurality of nodes which are interconnectedwith fibrils to form a node-fibril network such that the plurality ofvoids are formed between the nodes and interconnecting fibrils.

Another aspect of this method mode includes constructing an ablationelectrode to electrically couple to an electrical current source andalso to the permeable section when the pressurizeable fluid chamber isfilled with an electrically conductive fluid.

One variation of this aspect further includes securing the ablationelectrode to the distal end portion of the elongate catheter body, andsecuring the fluid permeable tube to the elongate catheter body onopposite sides of the ablation electrode such that the ablationelectrode is positioned within the fluid chamber.

Another aspect of this method mode includes constructing the fluidpermeable tube such that both the permeable and non-permeable sectionsare formed at least in part from the porous material.

One variation of this aspect includes forming the fluid permeable tubesuch that the plurality of pores are provided along both the permeableand the non-permeable sections, and substantially blocking the poresalong the non-permeable section such that the blocked pores aresubstantially non-permeable to the volume of fluid when the fluid ispressurized.

One more particular embodiment of this variation includes blocking thepores along the non-permeable section with an insulator material, suchas by dip coating the non-permeable section with the insulator material,melting the insulator material to the non-permeable section, ordepositing the insulator material along the non-permeable section.

Another more particular embodiment of the insulating variation includessubstantially blocking the pores along both the permeable section andthe non-permeable section with the insulator material, and thenselectively removing the insulator material such that the pores alongthe permeable section are left open and un-blocked and the pores alongthe non-permeable section are left blocked. The insulation may beselectively removed in one beneficial method by dissolving the insulatormaterial along the permeable section with a solvent, which process mayfurther include selectively masking the insulator material along thenon-permeable section from being exposed to and dissolved by thesolvent.

Another mode of the invention includes a method for treating a region oftissue within a body by expanding a balloon from a radially collapsedcondition to a radially expanded condition with a volume of pressurizedfluid within a fluid chamber defined at least in part by the balloon,forcing the pressurized fluid from within the fluid chamber andoutwardly from the balloon through a plurality of pores provided along apermeable section of the balloon, and substantially blocking thepressurized fluid from passing outwardly from and through the balloonalong a non-permeable section of the balloon.

One aspect of this method further includes engaging the permeablesection with a region of tissue and then forcing the pressurized fluidoutwardly from the balloon through the pores along the permeable sectionand into the region of tissue. Further to this aspect, the pressurizedfluid is forced outwardly from the balloon through the permeable sectionby weeping the fluid into the region of tissue without formingpressurized jets of fluid into the region of tissue.

Another aspect of this method includes engaging the permeable sectionwith a circumferential region of tissue along a body space wall whichdefines at least in part a body space, and then forcing the pressurizedfluid outwardly from the balloon through the pores along the permeablesection and in a circumferential pattern into the circumferential regionof tissue. One beneficial variation of this aspect of the methodincludes engaging the permeable section with a circumferential region oftissue along a pulmonary vein or with a circumferential region of tissuethat surrounds a pulmonary vein ostium along a posterior left atrialwall. Another beneficial variation includes electrically coupling anablation electrode to the pressurized fluid which is an electricallyconductive fluid, and ablating the circumferential region of tissue withthe pressurized fluid as it passes outwardly form the balloon throughthe permeable section and into the circumferential region of tissue.Further to this variation, the fluid may be passed to thecircumferential region of tissue while substantially shielding theadjacent regions of tissue from electrically coupling to the ablationelectrode via the pressurized fluid as it passes outwardly from theballoon through the permeable section and into the circumferentialregion of tissue. A further more detailed embodiment of this shieldingvariation includes radially engaging the non-permeable section with anadjacent region of tissue adjacent to the circumferential region oftissue engaged with the permeable section. This more detailed embodimentof the method may further include radially engaging a secondnon-permeable section with a second adjacent region of tissue that isadjacent to the circumferential region of tissue opposite the firstadjacent region of tissue.

Another mode of the invention provides a circumferential ablation memberwith an expandable member constructed of two expandable elements alongeach of two end portions of the expandable member and a tubular memberextending between the expandable elements which includes acircumferential band that is fluid permeable, wherein a fluid chamber isformed by the expandable elements and the tubular member extendingtherebetween, and such that fluid from the fluid chamber may beablatively coupled to a circumferential region of tissue engaged by thecircumferential band.

In one aspect of this mode, an electrode is adapted to be electricallycoupled to the fluid within the chamber and thus to tissue engaged bythe permeable circumferential band. In one variation of this aspect, theelectrode is provided along an internal catheter shaft extending betweenthe expandable elements.

In another mode, a medical catheter assembly has an expandable memberthat encloses a fluid chamber and also an inner expansion element suchthat the expansion element is adapted to expand a first portion of theexpandable member's working length to a different outer diameter than asecond portion of the working length.

In one aspect of this mode, the working length of the expandable memberfurther comprises a circumferential band that is permeable to the fluidwithin the fluid chamber.

In another aspect of this mode, the expandable member encloses first andsecond inner expansion elements. A tubular wall extends between thoseouter surfaces to enclose the fluid chamber. The working length of theexpandable member includes an intermediate region constructed of thetubular wall, and also first and second end portions on opposite sidesof the intermediate region, wherein the first and second inner expansionelements are located along the first and second end portions.

In a further variation of this aspect, the inner expansion elements areadapted to expand to different outer diameters such that the workinglength is tapered between the first and second end portions, and moreparticularly in one variation so that the working length has a distallyreducing outer diameter.

In another mode, a circumferential ablation device assembly and methodprovide an elongate body with a circumferential ablation member on thedistal end portion that includes a first expandable member, and a secondexpandable member is further provided along the distal end portion in alongitudinally spaced location relative to the first expandable member.An ablation element cooperates with at least one of the first and secondexpandable members in order to ablatively couple to tissue engagedtherewith in the expanded condition. In one particular aspect of thismode, the ablation element cooperates with the first expandable memberthat is distal to the second expandable member on the distal endportion, and ablatively couples to tissue engaged by the firstexpandable member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-E shows schematic views of different types of circumferentialpatterns according to the invention.

FIG. 2 shows a longitudinal cross-sectional view of one type ofcircumferential ablation device with a balloon ablation member that issecured to the distal end of an over-the-wire catheter and that has aworking length with a circumferential, ablative band disposed betweentwo insulated and non-ablative end portions.

FIGS. 3A-B show longitudinal cross-sectional and perspective views,respectively, of another circumferential ablation device having asimilar balloon ablation member as shown in FIG. 2, except showing theballoon ablation member secured to the distal end portion of a steerabledelivery member.

FIGS. 4A-C show various views of a circumferential ablation devicesimilar to that shown in FIGS. 3A-B, except showing the balloon ablationmember disposed around a steerable delivery member such that thesteerable delivery member is moveable within the balloon ablationmember.

FIGS. 5A-E variously show various modes of one method for manufacturinga balloon for use as a balloon ablation member according to theinvention.

FIGS. 6A-D variously show various modes of another method formanufacturing a balloon for use as a balloon ablation member accordingto the invention.

FIGS. 7A-D show schematic axial cross-sectional views of various typesof fold patterns for at least a portion of a balloon ablation member ina radially collapsed position according to the invention.

FIGS. 8A-C show perspective views of various modes of another method formanufacturing a balloon for use as a balloon ablation member accordingto the invention.

FIGS. 9A-C show longitudinal cross-sectional views, with respect toFIGS. 9A-B, and a perspective overview, with respect to FIG. 9C,illustrating various modes of another method for manufacturing a balloonfor use as a balloon ablation member according to the invention.

FIGS. 10A-E show various modes of another method for manufacturing aballoon for use as a balloon ablation member according to the invention.

FIGS. 11A-C show a side perspective view and two axial cross-sectionalviews, respectively, of a final balloon ablation member, wherein acircumferential ablative band provided along the working length of theballoon is shown in a folded configuration when the balloon is in aradially collapsed condition.

FIG. 11D shows a radially expanded condition for a balloon ablationmember such as that shown in FIGS. 11A-C.

FIG. 12A shows a schematic view of the microscopic structure for onetype of expanded fluoropolymer for use in forming a porouscircumferential band along a balloon of a circumferential ablationmember according to the invention.

FIG. 12B shows a schematic view of a similar microscopic fluoropolymerstructure as that shown in FIG. 12A, except further showing theinclusion of a filler substrate within void or pore regions in thenode-fibril network of the expanded fluoropolymer.

FIGS. 12C-D compare schematic views of the microscopic structures forone type of uniformly expanded polytetrafluoroethylene (PTFE) materialand another type of selectively expanded polytetrafluoroethylene (PTFE)material.

FIGS. 13A-B show various modes of using one type of circumferentialablation device in order to ablate a circumferential region of tissue ata location where a pulmonary vein extends from an atrium according toone mode of the invention.

FIG. 13C shows a sectional view of a circumferential conduction block ina pulmonary vein as formed by a circumferential ablation device such asaccording to the modes shown in FIGS. 13A-B.

FIGS. 14A-B show various modes of using a circumferential ablationdevice to ablate a circumferential region of tissue along a locationwhere a pulmonary vein extends from an atrium according to another modeof the invention.

FIG. 14C shows a sectional view of a circumferential conduction block ina pulmonary vein as formed by a circumferential ablation device such asaccording to the modes shown in FIGS. 14A-B.

FIGS. 15A shows one mode of using another circumferential ablationdevice according to the present invention in order to ablate acircumferential region of tissue along an atrial wall and surrounding apulmonary vein ostium.

FIG. 15B shows a perspective view of a circumferential ablation memberfor use according to the ablation device shown in FIG. 15A, and shows a“pear”-shaped balloon with an ablative circumferential band located atleast in part along a “distal-looking” face along a contoured taper ofthe balloon.

FIG. 15C shows a sectioned perspective view of a circumferentialconduction block formed according to the method and device shown inFIGS. 15A-B along the posterior left atrial wall and surrounding thepulmonary vein ostium.

FIGS. 16A-B show sequential modes of use of a dual-ablation balloonsystem for ablating two circumferential regions of tissue at twolocations, respectively, where two adjacent pulmonary vein branches,also respectively, extend from an atrial wall.

FIG. 17 shows a further shape for an expandable member according to thetissue ablation devices and procedures according to the invention.

FIG. 18 shows a further shape for an expandable member according to theinvention.

FIG. 19A shows a circumferential ablation member of the invention whichincludes a tapered expandable member with two inner expansion elementsand a tubular wall extending therebetween to form an inner fluid chamberthat is adapted to ablatively couple to tissue engaged along the tubularwall.

FIGS. 19B-C shows the circumferential ablation member shown in FIG. 19Ain sequential modes of use for positioning the circumferential ablationmember at a desired location for ablatively coupling an ablation elementwithin the expandable member to tissue at a location where a pulmonaryvein extends from an atrium.

FIG. 20 shows a circumferential ablation member of the invention whichincludes a tapered expandable member with an outer skin that enclosesone inner expansion element for expanding a portion of the workinglength of the outer skin to a larger outer diameter than another portionof the working length.

FIG. 21 shows a circumferential ablation member on the distal end of acatheter with a first expandable member and a second expandable memberand an ablation element within the first expandable member.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

Particular Definitions

Various terms are defined throughout this specification, and the meaningof any particular term is to be understood in the context of this entiredocument, in addition to the context of a particular description or usegiven in a specific circumstance as described hereunder. Such terms areto be understood as follows:

The terms “circumference” or “circumferential”, including derivativesthereof, are herein intended to mean a continuous path or line whichforms an outer border or perimeter that surrounds and thereby defines anenclosed region of space. Such a continuous path starts at one locationalong the outer border or perimeter, and translates along the outerborder or perimeter until it is completed at the original startinglocation to enclose the defined region of space. The related term“circumscribe,” including derivatives thereof, is herein intended tomean to enclose, surround, or encompass a defined region of space.Therefore, according to these defined terms, a continuous line which istraced around a region of space and which starts and ends at the samelocation “circumscribes” the region of space and has a “circumference”which is defined by the distance the line travels as it translates alongthe path circumscribing the space.

Still further, a circumferential path or element may include one or moreof several shapes, and may be, for example, circular, oblong, ovular,elliptical, or otherwise planar enclosures. A circumferential path mayalso be three dimensional, such as, for example, two opposite-facingsemi-circular paths in two different parallel or off-axis planes thatare connected at their ends by line segments bridging between theplanes.

For purpose of further illustration, FIGS. 1A-D therefore show variouscircumferential paths A, B, C, and D, respectively, each translatingalong a portion of a pulmonary vein wall and circumscribing a definedregion of space, shown at a, b, c, and d also respectively, eachcircumscribed region of space being a portion of a pulmonary vein lumen.For still further illustration of the three-dimensional circumferentialcase shown in FIG. 1D, FIG. 1E shows an exploded perspective view ofcircumferential path D as it circumscribes multiplanar portions of thepulmonary vein lumen shown at d′, d″, and d′″, which together make upregion d as shown in FIG. 1D.

The term “transect”, including derivatives thereof, is also hereinintended to mean to divide or separate a region of space into isolatedregions. Thus, each of the regions circumscribed by the circumferentialpaths shown in FIGS. 1A-D transects the respective pulmonary vein,including its lumen and its wall, to the extent that the respectivepulmonary vein is divided into a first longitudinal region located onone side of the transecting region, shown, for example, at region “X” inFIG. 1A, and a second longitudinal region on the other side of thetransecting plane, shown, for example, at region “Y” also in FIG. 1A.

Therefore, a “circumferential conduction block” according to the presentinvention is formed along a region of tissue which follows acircumferential path, such as along the pulmonary vein wall andcircumscribing the pulmonary vein lumen and transecting the pulmonaryvein relative to electrical conduction along its longitudinal axis. Thetransecting circumferential conduction block therefore isolateselectrical conduction between opposite longitudinal portions of thepulmonary wall relative to the conduction block and along thelongitudinal axis.

The terms “ablate” or “ablation,” including derivatives thereof, arehereafter intended to mean the substantial altering of the mechanical,electrical, chemical, or other structural nature of tissue. In thecontext of intracardiac ablation applications shown and described withreference to the variations of the illustrative embodiment below,“ablation” is intended to mean sufficient altering of tissue propertiesto substantially block conduction of electrical signals from or throughthe ablated cardiac tissue.

The term “element” within the context of “ablation element”, includingderivatives thereof, is herein intended to mean a discrete element, suchas an electrode, or a plurality of discrete elements, such as aplurality of spaced electrodes, which are positioned so as tocollectively ablate a region of tissue.

Therefore, an “ablation element” according to the defined terms mayinclude a variety of specific structures adapted to ablate a definedregion of tissue. For example, one suitable ablation element for use inthe present invention may be formed, according to the teachings of theembodiments below, from an “energy emitting” type that is adapted toemit energy sufficient to ablate tissue when coupled to and energized byan energy source. Suitable “energy emitting” ablation elements for usein the present invention may therefore include, for example: anelectrode element adapted to couple to a direct current (“DC”) oralternating current (“AC”) current source, such as a radiofrequency(“RF”) current source; an antenna element which is energized by amicrowave energy source; a heating element, such as a metallic elementor other thermal conductor which is energized to emit heat such as byconvective or conductive heat transfer, by resistive heating due tocurrent flow, or by optical heating with light; a light emittingelement, such as a fiber optic element which transmits light sufficientto ablate tissue when coupled to a light source; or an ultrasonicelement such as an ultrasound crystal element which is adapted to emitultrasonic sound waves sufficient to ablate tissue when coupled to asuitable excitation source.

In addition, other elements for altering the nature of tissue may besuitable as “ablation elements” under the present invention when adaptedaccording to the detailed description of the invention below. Forexample, a cryoablation element adapted to sufficiently cool tissue tosubstantially alter the structure thereof may be suitable if adaptedaccording to the teachings of the current invention.

Furthermore, a fluid ablation element, such as a wall that is porous orhas a discrete port (or a plurality of ports) which is fluidly coupledto a fluid delivery source, may be adapted to couple an ablation mediumto the tissue for ablation. In one aspect, the fluid ablation elementmay infuse the ablation medium, such as a fluid containing alcohol,directly into the tissue adjacent to the wall in order to substantiallyalter the nature of that tissue. In another aspect, the fluid ablationelement may supply radiofrequency or other mode of electrical current tothe tissue by electrically coupling an electrical ablation element tothe tissue via an ablation medium which is an electrically conductivefluid, such as for example an ionic fluid which may be, in oneillustrative variation, hypertonic saline. Moreover, the terms “ablationmedium” is intended to mean a medium that cooperates with one or more ofthe assemblies herein described in order to directly couple to andablate the intended tissue.

The terms “porous” or “permeable”, including derivatives thereof, areherein used interchangeably and are intended to mean a material wallconstruction having sufficient void volume to allow a substance topermeate into and across the wall, including allowing for such substrateto elude through and out from the wall, such as by weeping or in fluidjets, or by merely “absorbing” the substrate into the void volume in thewall wherein substantial flow of the substrate completely through andfrom the wall is substantially limited or even prevented. Examples of“porous” or “permeable” materials for the purpose of illustrationinclude without limitation: a material wall with inherent void volumeupon formation of the wall; a material wall that is not inherentlyporous but with apertures formed therethrough such as for example bymechanical drilling or laser/optical drilling; and a material wall withchemically formed void volume.

Design, Manufacture, and Use of Particular Embodiments

One circumferential ablation element design that is believed to providea highly useful embodiment of the present invention is shown in FIG. 2.As described in further detail below, this and other circumferentialablation element designs are believed to be particularly useful fortissue ablation along a region where a pulmonary vein extends from aleft atrium in the treatment of atrial fibrillation. As shown in FIG. 2,the design includes a circumferential ablation member (200) with twoinsulators (202,204) that encapsulate the proximal and distal ends,respectively, of the working length L of an expandable member (210). Inthe particular embodiment shown, the insulators (202,204) are distinctlayers of material that cover a balloon skin (212) of balloon orexpandable member (210). By providing these spaced insulators, acircumferential band (203) of uninsulated balloon skin is locatedbetween the opposite insulators.

The expandable member (210) as shown in FIG. 2 is joined at its proximalend to elongate body (201) that extends proximal to the expandablemember (210). More particularly, FIG. 2 shows the expandable member(210) and the elongate body (201) as being integrally formed, with theelongate body (201) extending from the expandable member (210) to theproximal end of the device outside of the patient (not shown). Thedistal end of the expandable member (210) is mounted to inner member(221) that extends through the elongate body (201) and expandable member(210) to the proximal end of the device. A lumen within the inner member(221) allows passage of a guidewire, as described in further detailbelow. The lumen defined between the elongate body (201) and the innermember (221) provides a passageway for fluids used in ablation and/orinflation of balloon (210). It will be appreciated that other designsmay also be used for the circumferential ablation member. For instance,the expandable member (210) need not be integral with the elongate body(201), and may be separately mounted.

It is further noted that this embodiment is not limited to a particularplacement of the ablation element. Rather, a circumferential band may beformed anywhere along the working length of the expandable member andcircumscribing the longitudinal axis of the expandable member aspreviously described.

The balloon construction shown in FIG. 2 forms a RF ablation electrode.An electrode (220) is provided on inner member (221) and is coupled toan ablation actuator shown at radiofrequency (“RF”) current source (230)via electrical lead (225), thereby forming an internal current sourcewithin balloon (210). RF current source (230) is coupled to both the RFelectrode element and also a ground patch (295) which is in skin contactwith the patient to complete a RF ablation circuit. A porous membranesuch as an expanded fluoropolymer, and more particularly an expandedpolytetrafluoroethylene material, comprises the entire balloon skin(212) of expandable member (210). The porous skin (212) may beconstructed according to several different methods, such as by formingholes in an otherwise contiguous polymeric material, includingmechanically drilling or using laser energy, or the porous skin maysimply be an inherently permeable material with inherent void volumeforming pores for permeability, as will be developed according to moreparticular illustrative embodiments below. By insulating the proximaland distal end portions of the working length of the expandable memberas shown in FIG. 2, only the pores along the circumferential band of theuninsulated intermediate region are allowed to ablatively couple theelectrolyte which carries an ablative RF current into tissue. Thisuninsulated intermediate region thus forms a permeable section, whilethe insulated regions of the expandable member are non-permeablesections.

It will further be appreciated that in the illustrated embodiment wherethe balloon (210) is integral with the elongate body (201), the elongatebody (201) is nonporous to prevent fluid from passing through the wallof the elongate body (201) before reaching the balloon chamber. Inanother embodiment, the insulator (202) may extend over the elongatebody (201) to insulate the elongate body (201). Further detailsregarding methods and apparatus for making a device permeable in certainportions and non-permeable in other portions are described below.

According to operation of the FIG. 2 assembly, an ablative fluid mediumthat is electrically conductive, such as for example a hypertonic salinesolution, passes from a source (240) and into the internal chamberdefined by the skin and outwardly into the porous wall of the balloonskin along the intermediate region until the solution directly couplesto tissue. By electrically coupling the fluid within the porous balloonskin to an RF current source (230) via electrode (220), the porousregion of the expandable member functions as an RF electrode wherein RFcurrent flows outwardly into the tissue engaged by the balloon via theconductive fluid absorbed into the porous intermediate region of thewall.

The ablation actuator mechanism for the overall assembly, such asincluding current source (230), may also include or be coupled to amonitoring circuit (not shown) and/or a control circuit (not shown)which together use either the electrical parameters of the RF circuit ortissue parameters such as temperature in a feedback control loop todrive current through the electrode element during ablation. Also, wherea plurality of ablation elements or electrodes in one ablation elementare used, a switching means may be used to multiplex the RF currentsource between the various elements or electrodes.

In addition, one further illustrative embodiment (not shown) which isalso contemplated provides an outer skin with the selectively porousintermediate region externally of another, separate expandable member,such as a separate expandable balloon, wherein the conductive fluidcoupled to a current source is contained in a region between the outerskin and the expandable member contained therein.

FIG. 2 broadly illustrates an ablation balloon construction wherein anablative surface is provided along the entire working length of anexpandable member, but the surface is shielded or insulated fromreleasing ablative energy into surrounding tissues except for along anunshielded or uninsulated equatorial band. As such, the insulatorembodiment contemplates other ablation elements which are provided alongthe entire working length of an expandable member and which areinsulated at their ends to selectively ablate tissue only about anuninsulated equatorial band. Other RF electrode arrangements are alsoconsidered suitable for use according to the selectively insulatedablation balloon embodiment shown in FIG. 2. In one further illustrativeexample, a metallized balloon includes a conductive balloon skin whereinthe electrical insulators, such as polymeric coatings, are positionedover or under each end of the working length and thereby selectivelyablate tissue with electricity flowing through the uninsulatedequatorial band. The balloon skin may itself be metallized, such as bymixing conductive metal, including but not limited to gold, platinum, orsilver, with a polymer to form a compounded, conductive matrix as theballoon skin. Or a discrete electrode element may be secured onto anouter surface of the balloon skin, such as in the embodiment when anexpandable balloon is placed within an outer skin of selected porosityas just described above. In another example, the porous aspects of thecircumferential band are beneficially applied in a chemical ablationelement mode, wherein a chemically ablative fluid medium such as analcohol based medium is absorbed within the wall of the circumferentialband and coupled to the tissue engaged to the band for ablation.

In the alternative, or in addition to the RF electrode variations justdescribed, the circumferential ablation member provided by the ablationballoon described may also include other ablative energy sources orsinks, and particularly may include a thermal conductor thatcircumscribes the outer circumference of the working length of anexpandable member. Examples of suitable thermal conductor arrangementsinclude a metallic element that may, for example, be constructed aspreviously described for the more detailed RF embodiments above.However, in the thermal conductor embodiment such a metallic elementwould be generally either resistively heated in a closed loop circuitinternal to the catheter, or conductively heated by a heat sourcecoupled to the thermal conductor. In the latter case of conductiveheating of the thermal conductor with a heat source, the expandablemember may be, for example, a polymeric balloon skin which is inflatedwith a fluid that is heated either by a resistive coil or by bipolar RFcurrent. In any case, it is believed that a thermal conductor on theouter surface of the expandable member is suitable when it is adapted toheat tissue adjacent thereto to a temperature between 40 deg and 80 degCelsius.

The various alternative ablation elements such as those just describedmay further incorporate the various other embodiments such as methods ofmanufacture or use described below, and fall within the presentinvention.

It is further contemplated that the insulators described may be onlypartial and still provide the relatively isolated ablative tissuecoupling along the circumferential band. For instance, in the conductiveRF electrode balloon case, a partial electrical insulator will allow asubstantial component of current to flow through the uninsulated portiondue to a “shorting” response to the lower resistance in that region. Inanother illustrative construction, balloon skin (212) may be thermallyconductive to surrounding tissue when inflated with a heated fluid whichmay contain a radiopaque agent, saline fluid, ringers lactate,combinations thereof, or other known fluids having acceptable heattransfer properties for these purposes.

FIG. 2 further shows use of an electrode element (220) as a radiopaquemarker to identify the location of the equatorial band (203) in order tofacilitate placement of that band at a selected ablation region of apulmonary vein via X-ray visualization. Electrode element (220) isopaque under X-ray, and may be constructed, for example, of a radiopaquemetal such as gold, platinum, or tungsten, or may comprise a radiopaquepolymer such as a metal loaded polymer. FIG. 2 shows electrode element(220) positioned coaxially over an inner tubular member (221) which isincluded in a coaxial catheter design as would be apparent to one ofordinary skill. The present invention contemplates the combination ofsuch a radiopaque marker additionally in the other embodiments hereinshown and described. To note, when the circumferential ablation memberthat forms an equatorial band includes a metallic electrode element,such electrode may itself be radiopaque and may not require use of aseparate marker. Moreover, various contemplated designs do not requirepositioning of the electrode (220) exactly along the band region, andtherefore such electrode may be replaced with a simple radiopaque markerin order to retain the ability to locate the band within the body viaX-ray visualization.

The expandable member of the embodiments shown may take one of severaldifferent forms, although the expandable member is generally hereinshown as an inflatable balloon that is coupled to an expansion actuatorwhich is a pressurizeable fluid source. The expandable member forms afluid chamber which communicates with a fluid passageway (not shown inall the figures) that extends proximally along the elongate catheterbody and terminates proximally in a proximal fluid port that is adaptedto couple to the pressurizeable fluid source.

The embodiment of FIG. 2 describes the expandable member (210) as beinga balloon made of a porous fluoropolymer, such as an expandedpolytetrafluoroethylene material It will be appreciated that variousother materials may also be suitable for the balloon, or portions of theballoon, as described for the various embodiments herein. Severalpossible balloon materials are described below. These materials may haveinherent porosity as would be known to one of skill in the art, or maybe made porous according to several different methods, such as formingholes in an otherwise contiguous polymeric material.

In one expandable balloon variation, the balloon or portion thereof may,be constructed of a relatively inelastic polymer such as a polyethylene(“PE”; preferably linear low density or high density or blends thereof),polyolefin copolymer (“POC”), polyethylene terepthalate (“PET”),polyimide, or a nylon material. In this construction, the balloon has alow radial yield or compliance over a working range of pressures and maybe folded into a predetermined configuration when deflated in order tofacilitate introduction of the balloon into the desired ablationlocation via known percutaneous catheterization techniques. In thisvariation, one balloon size may not suitably engage all pulmonary veinwalls for performing the circumferential ablation methods of the presentinvention on all needy patients. Therefore, it is further contemplatedthat a kit of multiple ablation catheters, with each balloon workinglength having a unique predetermined expanded diameter, may be providedfrom which a treating physician may choose a particular device to meet aparticular patient's pulmonary vein anatomy.

In an alternative expandable balloon variation, the balloon may beconstructed of a relatively compliant, elastomeric material, such as,for example (but not limited to), a silicone, latex, polyurethane, ormylar elastomer. In this construction, the balloon takes the form of atubular member in the deflated, non-expanded state. When the elastictubular balloon is pressurized with fluid such as in the previous,relatively non-compliant example, the material forming the wall of thetubular member elastically deforms and stretches radially to apredetermined diameter for a given inflation pressure. It is furthercontemplated that the compliant balloon may be constructed as acomposite, such as, for example, a latex or silicone balloon skin whichincludes fibers, such as metal, Kevlar, or nylon fibers, which areembedded into the skin. Such fibers, when provided in a predeterminedpattern such as a mesh or braid, may provide a controlled compliancealong a preferred axis, preferably limiting longitudinal compliance ofthe expandable member while allowing for radial compliance.

It is believed that, among other features, the relatively compliantvariation may provide a wide range of working diameters, which may allowfor a wide variety of patients, or of vessels within a single patient,to be treated with just one or a few devices. Furthermore, this range ofdiameters is achievable over a relatively low range of pressures, whichis believed to diminish a potentially traumatic vessel response that mayotherwise be presented concomitant with higher pressure inflations,particularly when the inflated balloon is oversized to the vessel. Inaddition, the low-pressure inflation feature of this variation issuitable for the present invention because the functional requirement ofthe expandable balloon is merely to engage the ablation element againsta circumferential path along the inner lining of the pulmonary veinwall.

According to one elastomeric construction that is believed to be highlybeneficial for engaging large pulmonary vein ostia, such as ranging from1-2.5 centimeters in diameter, the balloon is preferably constructed toexhibit at least 300% expansion at 3 atmospheres of pressure, and morepreferably to exhibit at least 400% expansion at that pressure. The term“expansion” is herein intended to mean the balloon outer diameter afterpressurization divided by the balloon inner diameter beforepressurization, wherein the balloon inner diameter before pressurizationis taken after the balloon is substantially filled with fluid in ataught configuration. In other words, “expansion” is herein intended torelate to change in diameter that is attributable to the materialcompliance in a stress-strain relationship. In one more detailedconstruction which is believed to be suitable for use in most conductionblock procedures in the region of the pulmonary veins, the balloon isadapted to expand under a normal range of pressure such that its outerdiameter may be adjusted from a radially collapsed position of about 5millimeters to a radially expanded position of about 2.5 centimeters (orapproximately 500% expansion ratio).

Moreover, a circumferential ablation member is adapted to conform to thegeometry of the pulmonary vein ostium, at least in part by providingsubstantial compliance to the expandable member, as will be furtherdeveloped below. Further to this conformability, such as is shown byreference to FIG. 14A, the working length L of expandable member (1470)is also shown to include a taper which has a distally reducing outerdiameter from a proximal end (1471) to a distal end (1473). In either acompliant or the non-compliant balloon, such a distally reducing taperedgeometry adapts the circumferential ablation element to conform to thefunneling geometry of the pulmonary veins in the region of their ostiain order to facilitate the formation of a circumferential conductionblock there.

Other expandable members than a balloon may also be suitable accordingto the insulator aspects of the invention. For example, various modes ofknown expandable cages may be sufficient expandable members for thisinvention so long as a fluid chamber is at least in part enclosed by orotherwise associated with the cage so as to provide for ablative fluidcoupling to tissue as broadly contemplated by the disclosed embodiments.

It is to be appreciated that the circumferential band (203) shown inFIG. 2 and elsewhere throughout the figures generally has a functionalband width w relative to the longitudinal axis of the working lengthwhich is only required to be sufficiently wide to form a completeconduction block against conduction along the walls of the pulmonaryvein in directions parallel to the longitudinal axis. In contrast, theworking length L of the respective expandable element is adapted tosecurely anchor the distal end portion in place such that the ablationelement is firmly positioned at a selected region of the pulmonary veinfor ablation. Accordingly, the band width w is relatively narrowcompared to the working length L of the expandable element, and theelectrode band may thus form a relatively narrow equatorial band whichhas a band width that is less than two-thirds or even one-half of theworking length of the expandable element. Additionally, it is to benoted here and elsewhere throughout the specification, that a narrowband may be placed at locations other than the equator of the expandableelement, preferably as long as the band is bordered on both sides by aportion of the working length L.

Further to the relatively narrow circumferential band aspect of theinvention, the circumferential lesion formed may also be relativelynarrow when compared to its own circumference, and may be less thantwo-thirds or even one-half its own circumference on the expandableelement when expanded. In one arrangement which is believed to besuitable for ablating circumferential lesions in heart chambers orpulmonary veins, the band width w is less than 1 cm with a circumferenceon the working length when expanded that is greater than 1.5 cm.

Still further to the FIG. 2 embodiment, energy is coupled to the tissuelargely via the ablative medium supplied by the inflation fluid andporous or permeable balloon skin. It is believed that, for in vivo usesof the present invention, the efficiency of energy coupling to thetissue, and therefore ablation efficiency, may significantly diminish incircumstances where there is poor contact and conforming interfacebetween the balloon skin and the tissue. Accordingly, several differentballoon types may be provided for ablating different tissue structuresso that a particular shape may be chosen for a particular region oftissue to be ablated, such as for example in order to accommodatediffering geometries encountered when ablating circumferential regionsof tissue to isolate various different pulmonary veins in either thesame of different patients, as further developed elsewhere hereunder,and by reference to FIGS. 17-21 below.

The elongate body (201) of the overall catheter assembly shown in FIG.2, and as appropriate elsewhere throughout this disclosure, may have anouter diameter provided within the range of from about 5 French to about10 French, and more preferable from about 7 French to about 9 French. In“guidewire tracking designs” as shown in FIG. 2, the guidewire lumenpreferably is adapted to slideably receive guidewires ranging from about0.010 inch to about 0.038 inch in diameter, and preferably is adaptedfor use with guidewires ranging from about 0.018 inch to about 0.035inch in diameter. Where a 0.035 inch guidewire is to be used, theguidewire lumen preferably has an inner diameter of 0.040 inch to about0.042 inch. In addition, the inflation lumen preferably has an innerdiameter of about 0.020 inch in order to allow for rapid deflationtimes, although the diameter may vary based upon the viscosity ofinflation medium used, length of the lumen, and other dynamic factorsrelating to fluid flow and pressure.

The elongate body (201) should also be adapted to be introduced into theleft atrium such that the distal end portion with balloon and transducermay be placed within the pulmonary vein ostium in a percutaneoustranslumenal procedure, and even more preferably in a transeptalprocedure as otherwise herein provided. Therefore, the distal endportion of the body (201) is preferably flexible and adapted to trackover and along a guidewire seated within the targeted pulmonary vein. Inone further more detailed construction which is believed to be suitable,the proximal end portion is adapted to be at least 30% stiffer than thedistal end portion. According to this relationship, the proximal endportion may be suitably adapted to provide push transmission to thedistal end portion while the distal end portion is suitably adapted totrack through bending anatomy during in vivo delivery of the distal endportion of the device into the desired ablation region.

Notwithstanding the specific device constructions just described, otherdelivery mechanisms for delivering the circumferential ablation memberto the desired ablation region are also contemplated. For example, whilethe FIG. 2 variation is shown as an “over-the-wire” catheterconstruction, other guidewire tracking designs may be suitablesubstitutes, such as, for example, catheter devices which are known as“rapid exchange” or “monorail” variations wherein the guidewire is onlyhoused coaxially within a lumen of the catheter in the distal regions ofthe catheter. In another example, a deflectable tip design may also be asuitable substitute and which is adapted to independently select adesired pulmonary vein and direct the transducer assembly into thedesired location for ablation.

Further to this latter variation, the guidewire lumen and guidewire ofthe FIG. 2 variation may be replaced with a “pullwire” lumen andassociated fixed pullwire which is adapted to deflect the catheter tipby applying tension along varied stiffness transitions along thecatheter's length. Still further to this pullwire variation, acceptablepullwires may have a diameter within the range from about 0.008 inch toabout 0.020 inch, and may further include a taper, such as, for example,a tapered outer diameter from about 0.020 inch to about 0.008 inch.

FIGS. 3A-B illustrate such an additional variation of the tissueablation device assembly (300) wherein an ablation balloon (310) isbeneficially secured over a steerable delivery member (302) which may besimilar for example to deflectable tip electrode catheter and/oraccording to various steerable cardiac electrophysiology mappingcatheters, such as those known in the art. Outer member (301) is showncoaxially disposed over steerable delivery member (302) such thatpermeable band (303) of balloon (310) provided by outer sheath (301) isdisposed around electrode (320) provided on the steerable deliverymember (302). Inflation device (340) is fluidly coupled with the innerfluid chamber formed by balloon (310) and includes a pressurized sourceof an ablative medium such as electrically conductive fluid. An ablationactuator, which in the FIG. 3A embodiment is RF current source (330), iscoupled with electrode (320). Furthermore, tip electrodemapping/actuator assembly (314) is also shown coupled with tip electrode(315) via tip electrode lead (313). Further to the particular variationshown in FIGS. 3A-B, the distal end of pullwire (311) is schematicallyshown to be secured to the distal end of the steerable delivery member(301), whereas the proximal end of pullwire (311) is shown coupled todeflection actuator (314) which is adapted to controllably provideforces on pullwire (311) such that the distal end of assembly (300) isdeflected or shaped as desired for torsional steering.

Balloon (310) is secured to the outer surface (321) of steerabledelivery member (302) via bond (305) such that a fluid tight seal isprovided and further such that balloon (310) and steerable deliverymember (302) are in a fixed relationship to each other such that theymay be manipulated and controllably positioned together viatranscatheter techniques. In a preferred mode for use shown in FIG. 3B,assembly (300) is shown delivered into a left atrium through atranseptal sheath (350), wherein it is shaped (illustrated by doubleheaded arrows in FIG. 3B) and positioned within a pulmonary vein. Morespecifically, band (303) is engaged to circumferential region of tissue(370) in order to ablatively couple electrode (320) through band (303)and to tissue (370) via the ablative fluid medium absorbed into the wallof band (303).

The electrode (320) need not be positioned exactly along band (303)relative to the long axis of device assembly (300) in order toelectrically couple the electrode to fluid and thereby to the band andtissue surrounding the band. However, as electrode (320) is preferably aradiopaque material such as a metal, and considering an increase inimpedance when moving electrode (320) further away from band (303), theembodiment shown is believed to be highly beneficial. If anotherelectrical source were provided such that there were no electrode (320)within balloon (310), then a separate radiopaque band may be provided ata similar location where electrode (320) is shown in FIG. 3A in order toprovide a marker to position band (303) where desired, such as alongcircumferential region of tissue (370) as shown in FIG. 3B.

The FIGS. 4A-C embodiment provides a steerable electrodecatheter/balloon assembly (400) that differs from the FIGS. 3A-Cembodiment in that the steerable delivery member (402) in FIGS. 4A-C ismoveably engaged within an interior passageway of a separate outermember (401) that provides balloon (410) in a separate sheath assemblythat surrounds steerable delivery member (402). Section A in FIG. 4Aindicates the portion of the outer member (401) that does not expandwhen filled with fluid, while Section B in FIG. 4B defines the balloonportion that does expand when filled with fluid. More specifically,outer member (401) is characterized as being: (a) closed at the distalend; and (b) inflatable along balloon (410) if pressurized with fluidfrom pressurizeable fluid source (440) containing electricallyconductive fluid. By advancing the steerable delivery member (402)within passageway (401′), electrode (420) is aligned with band (403)such that expansion of balloon (410) and actuation of electrode (420)ablates a circumferential band of tissue (470) engaged to band (403), asshown in FIG. 4B. Moreover, as in FIGS. 3A-C, the steerable deliverymember (402) is preferably of the deflectable variety known in the art,and therefore allows for controllable positioning of the balloon (410)before, during, or after expansion and circumferential ablation, whereinsuch deflection is shown for the purpose of illustration in FIG. 4C.Beneficially, however, this FIGS. 4A-C embodiment allows for the outermember (401) to be selectively fit over and used with any commerciallyavailable steerable catheters, such as for example commerciallyavailable, “deflectable tip” RF ablation catheters.

In order to add the proper positioning of the electrode (420) within theballoon (410) relative to band (403), some form of indicia may beprovided on either or both of outer and inner catheters of thisassembly, such as either visible markings on portions of the associatedmembers extending externally of the body, or radiopaque markers thatallow x-ray guided alignment of the assemblies.

FIGS. 5A-E show various modes for making a porous band along a workinglength of a circumferential ablation balloon. More specifically, FIGS.5A-5E show methods for post-processing a pre-formed balloon that iseither totally porous (FIG. 5A) or totally non-porous (FIG. 5B),respectively, prior to post-processing. More specifically, FIG. 5C showsa method wherein the totally porous balloon of FIG. 5A is exposed to afilling agent, such as in a dip-coating or other deposition method.

FIG. 5C illustrates the method for treating the totally porous startingballoon of FIG. 5A. Intermediate region (503) is masked off andinsulated from being filled during the deposition procedure, andthereafter is left porous when the insulator is removed after filling,leaving only the uninsulated ends non-porous due to the filler (505)introduced into the pores there. In contrast, FIG. 5D illustrates themethod using a totally non-porous balloon material from FIG. 5B andmasks end portions (502) and (504) while intermediate region or band(503) is left uninsulated and exposed. The bath shown in shadow in FIG.5D contains not filler for filling the pores along the balloon as wasjust illustrated for FIG. 5C, but instead contains a solvent (506) thatremoves material where exposed to the balloon, for example from filledpores to be cleansed and opened for fluid flow.

The method just described for selectively masking the intermediateregion and then exposing the entire balloon to filler may be modified.Without masking the porous balloon, the two end portions of the balloonmay be dipped into a filler, such that the intermediate region is“undipped” or left out of the dipping material and the only region leftporous according to the invention.

The method illustrated by reference to FIGS. 6A allows for the formationof the discrete intermediate permeable band (603) when a base product ortube (600) of a non-expanded, relatively non-permeable fluoropolymer orsimilar material is used. More specifically, FIG. 6B shows tube (600)being stretched (see illustrative arrows) while only intermediate region(603) is being heated, at the exclusion of end portions (602) and (604)in order to isolate deformation along that intermediate region (603).Such deformation is known to “expand” the substrate fluoropolymer suchthat the node and fibril network is stretched with larger void volumesthan in the relatively “un-expanded” end portions. Accordingly,intermediate region (603) is left as a circumferential, permeable bandof expanded fluoropolymer. The end portions of such selectively expandedtube may be incorporated onto a delivery and ablation source assemblysuch as according to the embodiments elsewhere herein described, such asby forming the tube into a balloon (610) as shown in FIG. 6D and thenadapting it to the distal end of an over-the-wire ablation catheterassembly or deflectable tip inner electrode catheter. Sincefluoropolymer is generally inelastic, such a balloon may beneficially befolded for in vivo delivery to the left atrium and pulmonary vein.Examples of such folds are variously shown throughout FIGS. 7A-D.

Fluid permeable fluoropolymer such as polytetrafluoroethylene may alsobe provided only along the intermediate region, wherein the end portionsof the working length of the ablation balloon are formed from anothermaterial grafted or otherwise secured to the permeable intermediatematerial, as variously shown by example and without limitation in FIGS.8A-10E.

More specifically FIGS. 8A-C show a method for constructing such aballoon with varied material composition over the working length. FIG.8A shows a mandrel (800) with an enlarged region (802) sized to supportpermeable tubing (810) which may be for example a fluoropolymer such asan expanded PTFE material. An elastic member (820) is advanced over onenarrow end of mandrel (800) until it elastically is forced open as it isadvanced over the enlarged region (802) and further over permeabletubing (810) to create an overlap zone (825), as shown in FIG. 8B. Thesame is done on the opposite side, as shown in FIG. 8C, to produce thefinal grafted balloon, having a second elastic end portion (830), whichmay be then removed from the mandrel.

This particular method just described may be varied, such as for exampleas is shown in FIGS. 9A-B wherein the end portions (920,930) areprovided over the mandrel (902) first, and then the PTFE membrane (910)is provided over the end portions to form the requisite overlap zones toresult in a contiguous balloon (FIG. 9C).

According to the methods illustrated in one mode in FIGS. 8A-C and inanother mode in FIGS. 9A-C, the elastomeric end portions may be bondedto the permeable membrane along the intermediate region according to avariety of methods. In one variation, the end portions are thermoplasticpolymers which may be melted and then flow into the pores of thepermeable membrane. However, a separate bonding agent such as a solventbonding agent or an adhesive may also be used to accomplish the bondingalong the overlap region, as is shown by use of bonding agent (1012) byreference to FIGS. 10A-D in a similar method to that shown in FIGS.8A-C. FIG. 10E shows balloon (1000) being removed from the mandrel(1002) after formation according to the method illustrated in FIGS.10A-D, and further illustrates the novel result of the present methodwhich provides a balloon having elastomeric end portions (1020, 1030)with a relatively non-elastomeric intermediate region (1010). Theoverlap between the end portions (1020, 1030) and intermediate region(1010) create an overlap zone (1025). This relationship is furtherillustrated in various views of balloon (1000) in FIGS. 11A-D, showingone mode for folding the relatively non-elastomeric intermediate region(1010) while the balloon is in a deflated or radially collapsedcondition in FIGS. 11A-C, and another mode for the assembly in theinflated or radially expanded condition in FIG. 11D.

FIGS. 12A-D show various modes of porous fluoropolymer, or morespecifically polytetrafluoroethylene (PTFE), which is believed to be ahighly beneficial material for use in the assemblies and methodsaccording to the present invention, and in particular the porouscircumferential band embodiments. More specifically, expanded PTFE asshown at porous material (1200) generally includes a plurality of nodes(1202) and interconnecting fibrils (1204) which form a network. In theFIG. 12A variation, between these nodes and fibrils are voids (1206)which provide the porosity or permeability desired for a particularapplication of the ablation assemblies and methods of the presentinvention. It will be appreciated that any of a number of different poresizes may be appropriate depending on the particular application.Accordingly, the specific material used for the application may beselected from a variety of commercially available materials havingdifferent pore sizes.

As further shown in FIG. 12B, the voids (1206) may also be filled with afiller (1208) such that permeability is attenuated or completelyblocked. U.S. Pat. No. 5,753,358 to Korleski, and U.S. Pat. No.5,766,750 to Korleski, the entirety of both of which are herebyincorporated by reference, disclose an adhesive composite materialcomprising an expanded fluoropolymer with nodes and interconnectedfibrils, the fluoropolymer having a void volume which is at leastpartially filled by any of a number of fillers. Any of the biocompatibleand nontoxic fillers disclosed in these patents might be appropriate foruse in accordance with the embodiments of the present invention. Such aconstruction may be appropriate for the methods of manufacturing anablation balloon as shown and described above by reference to FIGS.5A-E. For example, a starting material according to FIG. 12A may beprovided for the method illustrated by reference to FIGS. 5A and C,wherein intermediate region (503) is masked while filler (1208) fillsall the void volumes along end portions (502,504). The result is aconstruction along intermediate region (503) that is consistent withFIG. 12A, but a construction along end portions (502,504) that isconsistent with FIG. 12B. In contrast, the whole balloon may be filledin a construction consistent with FIG. 12B and then the fillerselectively moved from only the intermediate portion (503), yielding asimilar result just described.

A comparison of FIGS. 12C and D also further illustrates a selectiveporosity embodiment along a contiguous fluoropolymeric balloonconstruction (fluoropolymer integral along whole working length ofballoon), such as according to the method shown and described byreference to FIGS. 6A-D. More specifically considering the structureshown in FIG. 12D by reference to FIGS. 6A-D, end portions (602,604)shown in FIGS. 6C or D may have a material construction consistent withfor example the denser, less expanded region of compacted nodes (1202)designated by their distance D1 in FIG. 12D. The porous region (603)however would be representative of the more expanded region designatedby the inter-nodule distance D2 in FIG. 12D. Thus, by providing varyingregions of density and material “expansion” along the balloon workinglength, the selected intermediate region of permeability for ablationmay be achieved.

The embodiments just described are believed to be particularly useful incatheter assemblies which are specifically adapted for ablating tissuealong a region where a pulmonary vein extends from a left atrium in thetreatment of atrial fibrillation. Therefore, the assemblies and methodsof the present invention are also contemplated for use in combinationwith, or where appropriate in the alternative to, the various particularfeatures and embodiments shown and described in the following co-pendingU.S. Patent Applications that also address circumferential ablation at alocation where a pulmonary vein extends from an atrium: U.S. Ser. No.08/889,798 for “CIRCUMFERENTIAL ABLATION DEVICE ASSEMBLY” to Michael D.Lesh et al., filed Jul. 8, 1997; U.S. Ser. No. 08/889,835 for “DEVICEAND METHOD FOR FORMING A CIRCUMFERENTIAL CONDUCTION BLOCK IN A PULMONARYVEIN” to Michael D. Lesh, filed Jul. 8, 1997; U.S. Ser. No. 09/199,736for “CIRCUMFERENTIAL ABLATION DEVICE ASSEMBLY” to Chris J. Diederich etal., filed Feb. 3, 1998; and U.S. Ser. No. 09/260,316 for “DEVICE ANDMETHOD FOR FORMING A CIRCUMFERENTIAL CONDUCTION BLOCK IN A PULMONARYVEIN” to Michael D. Lesh. The disclosures of these references are hereinincorporated in their entirety by reference thereto. For the purpose offurther illustration, FIGS. 13A-15C show sequential modes for using acircumferential ablation catheter assembly in treating atrialfibrillation. Where use according to an “over-the-wire” delivery mode isherein shown and described, it is further contemplated that otherdelivery modes such as the deflectable steerable modes described abovereferring to FIGS. 3A-4C.

A patient diagnosed with atrial arrhythmia is treated according to oneembodiment of the present invention by forming a circumferentialconduction block using the device assemblies herein described. The term“diagnose”, including derivatives thereof, is intended to includepatients suspected or predicted to have atrial arrhythmia, in additionto those having specific symptoms or mapped electrical conductionindicative of atrial arrhythmia. In one aspect, a patient diagnosed withmultiple wavelet arrhythmia originating from multiple regions along theatrial wall may also be treated in part by forming the circumferentialconduction block, although as an adjunct to forming long linear regionsof conduction block between adjacent pulmonary vein ostia in aless-invasive “maze”-type catheter ablation procedure. In another aspectof the method using the present invention, a patient diagnosed withfocal arrhythmia originating from an arrhythmogenic origin or focus in apulmonary vein is treated according to this method when thecircumferential conduction block is formed along a circumferential pathof tissue that either includes the arrhythmogenic origin or is betweenthe origin and the left atrium. In the former case, the conduction blockdestroys the arrhythmogenic tissue at the origin as it is formed throughthat focus. In the latter case, the arrhythmogenic focus may stillconduct abnormally, although such aberrant conduction is prevented fromentering and affecting the atrial wall tissue due to the interveningcircumferential conduction block.

The sequential steps of a method for using the circumferential ablationdevice assembly according to one embodiment of the present invention informing a circumferential conduction block at a location where apulmonary vein extends from a posterior left atrial wall include:positioning a circumferential ablation element at an ablation regionalong the location; and thereafter ablating a continuous circumferentialregion of tissue along the location.

Further to one positioning aspect of the invention, a distal tip of aguiding catheter is first positioned within the left atrium according toa transeptal access method, which is further described in more detail asfollows. The right venous system is first accessed using the “Seldinger”technique, wherein a peripheral vein (such as a femoral vein) ispunctured with a needle, the puncture wound is dilated with a dilator toa size sufficient to accommodate an introducer sheath, and an introducersheath with at least one hemostatic valve is seated within the dilatedpuncture wound while maintaining relative hemostasis. With theintroducer sheath in place, the guiding catheter or sheath is introducedthrough the hemostatic valve of the introducer sheath and is advancedalong the peripheral vein, into the region of the vena cavae, and intothe right atrium.

Once in the right atrium, the distal tip of the guiding catheter ispositioned against the fossa ovalis in the intraatrial septal wall. A“Brockenbrough” needle or trocar is then advanced distally through theguide catheter until it punctures the fossa ovalis. A separate dilatormay also be advanced with the needle through the fossa ovalis to preparean access port through the septum for seating the guiding catheter. Theguiding catheter thereafter replaces the needle across the septum and isseated in the left atrium through the fossa ovalis, thereby providingaccess for object devices through its own inner lumen and into the leftatrium.

It is however further contemplated that other left atrial access methodsmay be suitable substitutes for using the circumferential ablationdevice assembly of the present invention. In one alternative variationnot shown, a “retrograde” approach may be used, wherein the guidingcatheter is advanced into the left atrium from the arterial system. Inthis variation, the Seldinger technique is employed to gain vascularaccess into the arterial system, rather than the venous, for example, ata femoral artery. The guiding catheter is advanced retrogradedly throughthe aorta, around the aortic arch, into the ventricle, and then into theleft atrium through the mitral valve.

Subsequent to gaining transeptal access to the left atrium as justdescribed, a guidewire is then advanced into a pulmonary vein, which isdone generally through the guiding catheter seated in the fossa ovalis.In addition to the left atrial access guiding catheter, the guidewireaccording to this variation may also be advanced into the pulmonary veinby directing it into the vein with a second sub-selective deliverycatheter (not shown) which is coaxial within the guiding catheter, suchas, for example, by using one of the directional catheters disclosed inU.S. Pat. No. 5,575,766 to Swartz, the entirety of which is herebyincorporated by reference. Or, the guidewire may have sufficientstiffness and maneuverability in the left atrial cavity to unitarilysubselect the desired pulmonary vein distally of the guiding catheterseated at the fossa ovalis.

Suitable guidewire designs for use in the overall circumferentialablation device assembly of the present invention may be selected frompreviously known designs, while generally any suitable choice shouldinclude a shaped, radiopaque distal end portion with a relatively stiff,torquable proximal portion adapted to steer the shaped tip under X-rayvisualization. Guidewires having an outer diameter ranging from 0.010″to 0.035″ may be suitable. In cases where the guidewire is used tobridge the atrium from the guiding catheter at the fossa ovalis, andwhere no other sub-selective guiding catheters are used, guidewireshaving an outer diameter ranging from 0.018″ to 0.035″ may be required.It is believed that guidewires within this size range may be required toprovide sufficient stiffness and maneuverability in order to allow forguidewire control and to prevent undesirable guidewire prolapsing withinthe relatively open atrial cavity. Subsequent to gaining pulmonary veinaccess, the distal end portion of a circumferential ablation deviceassembly is then tracked over the guidewire and into the pulmonary vein,followed by positioning a circumferential ablation element at anablation region of the pulmonary vein where the circumferentialconduction block is to be desirably formed.

FIG. 13A shows a circumferential ablation device system (1300) accordingto one embodiment of the present invention during use as just described,which circumferential ablation system (1300) includes a guiding catheter(1301), guidewire (1302), and circumferential ablation catheter (1303).

More specifically, FIG. 13A shows guiding catheter (1301) subsequent toperforming a transeptal access, and also shows guidewire (1302)subsequent to advancement and positioning within a pulmonary vein. FIG.13A shows circumferential ablation catheter (1303) as it trackscoaxially over guidewire (1302) with a distal guidewire tracking member,which is specifically shown only in part at first and second distalguidewire ports (1342,1344) located on the distal end portion (1332) ofan elongate catheter body (1330). A guidewire lumen (not shown) extendsbetween the first and second distal guidewire ports (1342,1344) and isadapted to slideably receive and track over the guidewire. In theparticular variation of FIG. 13A, the second distal guidewire port(1344) is located on a distal end portion (1332) of the elongatecatheter body (1330), although proximally of first distal guidewire port(1342).

As would be apparent to one of ordinary skill, the distal guidewiretracking member configuration shown in FIG. 13A and just described hasthe following attributes normally associated with “rapid exchange” or“monorail” catheters according to persons of ordinary skill. Forexample, such assembly may be easily slideably coupled to the guidewireexternally of the body in a “backloading” technique after the guidewireis first positioned in the pulmonary vein and without the need for extralong wires. Furthermore, this guidewire tracking variation removes theneed for a guidewire lumen in the proximal portions of the elongatecatheter body (1330), which allows for a reduction in the outer diameterof the catheter shaft in that region. Nevertheless, a catheter accordingto the invention may instead incorporate a design which places thesecond distal guidewire port on the proximal end portion of the elongatecatheter body, as would be normally associated with “over-the-wire”catheters according to one of ordinary skill.

In addition, the inclusion of a guidewire lumen extending within theelongate body between first and second ports, as provided in FIG. 13A,should not limit the scope of acceptable guidewire tracking membersaccording to the present invention. Other guidewire tracking memberswhich form a bore adapted to slideably receive and track over aguidewire are also considered acceptable, such as, for example, thestructure adapted to engage a guidewire as described in U.S. Pat. No.5,505,702 to Arney, the entirety of which is hereby incorporated byreference herein.

While the assemblies and methods shown variously throughout the Figuresinclude a guidewire coupled to a guidewire tracking member on thecircumferential ablation catheter, other detailed variations may also besuitable for positioning the circumferential ablation element at theablation region in order to form a circumferential conduction blockthere. For example, an alternative circumferential ablation catheter notshown may include a “fixed-wire”-type of design wherein a guidewire isintegrated into the ablation catheter as one unit. In anotheralternative assembly, the same type of sub-selective sheaths describedabove with reference to U.S. Pat. No. 5,575,766 to Swartz for advancinga guidewire into a pulmonary vein may also be used for advancing acircumferential ablation catheter device across the atrium and into apulmonary vein.

FIG. 13A also shows circumferential ablation catheter (1303) with acircumferential ablation element (1360) formed on an expandable member(1370). The expandable member (1370) is shown in FIG. 13A in a radiallycollapsed position adapted for percutaneous translumenal delivery intothe pulmonary vein. However, expandable member (1370) is also adjustableto a radially expanded position when actuated by an expansion actuator(1375), as shown in FIG. 13B. Expansion actuator (1375) may include, butis not limited to, a pressurizeable fluid source. According to theexpanded state shown in FIG. 13B, expandable member (1370) includes aworking length L relative to the longitudinal axis of the elongatecatheter body which has a larger expanded outer diameter OD than when inthe radially collapsed position. Furthermore, the expanded outerdiameter OD is sufficient to circumferentially engage the ablationregion of the pulmonary vein. Therefore, the terms “working length” areherein intended to mean the length of an expandable member which, whenin a radially expanded position, has an expanded outer diameter that is:(a) greater than the outer diameter of the expandable member when in aradially collapsed position; and (b) sufficient to engage a body spacewall or adjacent ablation region surrounding the expandable member, atleast on two opposing internal sides of the body space wall or adjacentablation region, with sufficient surface area to anchor the expandablemember.

Circumferential ablation element (1360) also includes a circumferentialband (1352) on the outer surface of working length L which is coupled toan ablation actuator (1390) at a proximal end portion of the elongatecatheter body (shown schematically). After expandable member (1370) isadjusted to the radially expanded position and at least a portion ofworking length L circumferentially engages the pulmonary vein wall inthe ablation region, the circumferential band (1352) of thecircumferential ablation element (1360) is actuated by ablation actuator(1390) to ablate the surrounding circumferential path of tissue in thepulmonary vein wall, thereby forming a circumferential lesion thatcircumscribes the pulmonary vein lumen and transects the electricalconductivity of the pulmonary vein to block conduction in a directionalong its longitudinal axis.

More specific to the porous balloon electrode embodiments of theinvention, RF energy is delivered to the circumferential region oftissue in part by delivering RF energy from the ablation actuator toelectrodes via electrical leads. At the same time, electricallyconductive fluid, such as saline, is directed into the fluid chamberformed by balloon and is absorbed into the void volume of permeablecircumferential band, whereby electrical current may flow from theelectrode, through the fluid, across the wall of balloon, and into thecircumferential region of tissue.

A perfusion lumen may be formed within the distal end portion (1332) ofelongate catheter body (1330). The perfusion lumen may for example beformed between a distal perfusion port, such as at distal guidewire port(1342), and a proximal perfusion port (1344) which may be formed throughthe wall of the elongate catheter body (1330) and communicate with theguidewire lumen (not shown) which also forms the perfusion lumen betweenthe distal and proximal perfusion ports. In the particular design shown,after the guidewire has provided for the placement of the ablationelement into the pulmonary vein, the guidewire is withdrawn proximallyof the proximal perfusion port (1344) (shown schematically in shadow) sothat the lumen between the ports is clear for antegrade blood flow intothe distal perfusion port (1342), proximally along the perfusion lumen,out the proximal perfusion port (1344) and into the atrium (perfusionflow shown schematically with arrows).

FIG. 13C shows the pulmonary vein (1351) after removing thecircumferential ablation device assembly subsequent to forming acircumferential lesion (1372) around the ablation region of thepulmonary vein wall (1353) according to the use of the circumferentialablation device assembly shown in stepwise fashion in FIGS. 13A-B.Circumferential lesion (1370) is shown located along the pulmonary veinadjacent to the pulmonary vein ostium (1354), and is shown to also be“transmural,” which is herein intended to mean extending completelythrough the wall, from one side to the other. Also, the circumferentiallesion (1370) is shown in FIG. 13C to form a “continuous”circumferential band, which is herein intended to mean without gapsaround the pulmonary vein wall circumference, thereby circumscribing thepulmonary vein lumen. Various other references to similar anatomicallocations or structures are elsewhere made throughout this disclosurewith similar reference numerals attached to the end of the respectivefigure number (e.g., expandable member 1370 in FIG. 13A is referred toas expandable member 1470 in FIG. 14A, and as expandable member 1570 inFIG. 15A).

It is believed, however, that circumferential catheter ablation with acircumferential ablation element according to the present invention mayleave some tissue, either transmurally or along the circumference of thelesion, which is not actually ablated, but which is not substantialenough to allow for the passage of conductive signals. Therefore, theterms “transmural” and “continuous” as just defined are intended to havefunctional limitations, wherein some tissue in the ablation region maybe unablated but there are no functional gaps which allow forsymptomatically arrhythmogenic signals to conduct through the conductionblock and into the atrium from the pulmonary vein.

Moreover, it is believed that the functionally transmural and continuouslesion qualities just described are characteristic of a completedcircumferential conduction block in the pulmonary vein. Such acircumferential conduction block thereby transects the vein, isolatingconduction between the portion of the vein on one longitudinal side ofthe lesion and the portion on the other side. Therefore, any foci oforiginating arrhythmogenic conduction which is opposite the conductionblock from the atrium is prevented by the conduction block fromconducting down into the atrium and atrial arrhythmic affects aretherefore nullified.

FIGS. 14A-B show a further variation in another embodiment of thepresent invention, wherein a circumferential ablation member (1450)includes a radially compliant expandable member (1470) which is adaptedto conform to a pulmonary vein ostium (1454) at least in part byadjusting it to a radially expanded position while in the left atriumand then advancing it into the ostium. FIG. 14A shows expandable member(1470) after being adjusted to a radially expanded position whilelocated in the left atrium (1450). FIG. 14B further shows expandablemember (1470) after being advanced into the pulmonary vein (1451) untilat least a portion of the expanded working length L of circumferentialablation member (1450), which includes a circumferential band (1452),engages the pulmonary vein ostium (1454). FIG. 14C shows a portion of acircumferential lesion (1472) which forms a circumferential conductionblock in the region of the pulmonary vein ostium (1454) subsequent toactuating the circumferential ablation element to form thecircumferential lesion.

In addition to conforming to the pulmonary vein ostium, expandablemember (1470) is also shown in FIG. 14B to engage a circumferential pathof tissue along the left posterior atrial wall that surrounds ostium(1454). Moreover, circumferential band (1452) of the circumferentialablation member is also thereby adapted to engage that atrial walltissue. Therefore, the circumferential conduction block formed accordingto the method shown and just described in sequential steps by referenceto FIGS. 14A-B, as shown in-part in FIG. 14C, includes ablating thecircumferential path of atrial wall tissue which surrounds ostium(1454). Accordingly, the entire pulmonary vein, including the ostium, isthereby electrically isolated from at least a substantial portion of theleft atrial wall which includes the other of the pulmonary vein ostia,as would be apparent to one of ordinary skill according to thesequential method steps shown in FIGS. 14A-B and by further reference tothe resulting circumferential lesion (1472) shown in FIG. 14C.

The lesion shown in FIG. 14C isolates the pulmonary vein, but is formedby ablating tissue surrounding the pulmonary vein, although while alsowithin the pulmonary vein. It is further contemplated that such lesionmay be formed only along the posterior left atrial wall and surroundingthe pulmonary vein ostium, without also ablating tissue along the lumenor lining of the pulmonary vein or ostium, depending upon the particularshape of the balloon and/or position and geometry of the ablative bandalong that balloon. In one aspect of this embodiment, the compliantnature of the expandable member may be self-conforming to the region ofthe ostium such that the circumferential band is placed against thisatrial wall tissue merely by way of conformability. s

According to a further example, a pear-shaped balloon with a distallyreducing outer diameter may provide a “forward-looking” face which, withthe ablative band provided along that forward-looking face, is adaptedto advance against such atrial wall tissue and ablate there. Such a pearshape may be preformed into the expandable member or balloon, or themember may be adapted to form this shape by way of controlled complianceas it expands, such as for example by the use of composite structureswithin the balloon construction. In any case, according to the“pear”-shaped variation, the circumferential band of the ablation memberis preferably placed along the surface of the contoured taper which isadapted to face the left posterior atrial wall during use, such as forexample according to the method illustrated by FIGS. 14A-B.

FIGS. 15A-C show such a pear-shaped ablation balloon in acircumferential ablation member assembly adapted to electrically isolatea pulmonary vein and ostium from a substantial portion of the leftposterior atrial wall, which embodiment isolates the pulmonary veinwithout also ablating tissue along the lumen or lining of the pulmonaryvein or ostium.

In more detail, FIG. 15A shows circumferential band (1552′) to have ageometry (primarily width) and position along expandable member (1570′)such that it is adapted to engage only a circumferential path of tissuealong the left posterior atrial wall which surrounds the pulmonary veinostium. In one aspect of this embodiment, the compliant nature of theexpandable member may be self-conforming to the region of the ostiumsuch that the circumferential band is placed against this atrial walltissue merely by way of conformability.

In another variation, a “pear”-shaped expandable member (1570) orballoon that includes a contoured taper may be suitable for useaccording to the FIG. 15A. embodiment, as is shown by way of example inFIG. 15B. Such a pear shape may be preformed into the expandable memberor balloon, or the member may be adapted to form this shape by way ofcontrolled compliance as it expands, such as for example by the use ofcomposite structures within the balloon construction. In any case,according to the “pear”-shaped variation, the circumferential band(1552) of the ablation member is preferably placed along the surface ofthe contoured taper which is adapted to face the left posterior atrialwall, around the pulmonary vein 1551, during use according to the methodillustrated by FIG. 15A. It is further contemplated that the ablationelement may be further extended or alternatively positioned along otherportions of the taper, such as is shown by example in shadow at extendedband (1552″) in FIG. 15B. Accordingly, the variation shown in FIG. 15Bto include extended band (1552″) may also adapt this particular deviceembodiment for use in forming circumferential conduction blocks alsoalong tissue within the pulmonary vein and ostium, such as according tothe previously described method shown in FIGS. 15A-C.

The tissue ablation device systems shown and described below byreference to FIGS. 16A-21 are also believed to be beneficial forablating tissue at certain locations where one or more pulmonary veinsextend from an atrium.

The tissue ablation device system (1600) shown in FIGS. 16A-B includestwo circumferential ablation devices (1630,1640) in two pulmonary veinbranches (1610,1620) which form adjacent ostia along an atrial wall.Each of devices (1630,1640) has a circumferential ablation member(1632,1642), respectively, which is shown to include an expandablemember (1635,1645), also respectively, and an ablative energy source(1637,1647), also respectively. Each respective ablative energy source(1637,1647) is adapted to ablatively couple to a circumferential regionof tissue at the base of the respective pulmonary vein (1610,1620), andif properly positioned, may combine to ablate tissue between theadjacent veins (1610,1620), as shown specifically in FIG. 16B whereinthe expandable members expand the veins (1610,1620) to bring themtogether to assist the combined ablative coupling from each device tothe tissue therebetween.

Pulmonary veins have also been observed to present a thickened cuff oftissue at their respective ostia, which thickened cuff is believed topresent a unique resistance to expansion of an expandable member with aworking length extending from the atrium, across the ostia, and into themore compliant vein adjacent the ostium. Therefore, one embodiment ofthe invention further contemplates an expandable balloon having a shapewith a waist which assists the balloon to seat at the thickened, lesscompliant ostium and position the ablative circumferential band of theablation assembly there. Such an embodiment is shown in FIG. 17, whereindevice (1700) is shown with a circumferential ablation member (1710)having an expandable member (1720) that is a balloon with a narrowedwaist (1723) between two larger end portions (1720,1724) of the workinglength. As shown, distal end portion (1724) of the balloon's workinglength expands with the vein wall, and proximal end portion (1720) ofthe balloon's working length expands to a relatively large outerdiameter as the ostium becomes atrium. However, waist (1723) with itsreduced diameter allows the assembly to seat at the thicker ostium withablation element (1730) well positioned to ablatively couple throughexpandable member (1720) and into the circumferential region of tissuealong the ostium, such as for example according to the balloonembodiments with a permeable circumferential band as described above.

Various particular material constructions may be used for a balloon suchas just described for FIG. 17, in addition to particular ablationelement/expandable member configurations, and still benefit by the“peanut” or waisted balloon shape with regards to pulmonary vein ostiumablation. In particular with regards to material construction, either asubstantially compliant or elastomeric balloon material, or asubstantially non-compliant or non-elastomeric variety may be used. Or,a combination balloon construction with elastomeric/compliant andnon-elastomeric/non-compliant regions along the working length, such asherein described, may be suitable.

In addition, various modifications of the respective sizes anddimensions for the end portions and reduced diameter intermediate waistregion are also contemplated. For example, FIG. 18 shows a furtheriteration of a “waisted” balloon shape for circumferential ablationmember (1810), and in particular shows distal shoulder (1824) ofexpandable member or balloon (1820) having a steeper angled taper(1824′) onto the distal adaption to the underlying catheter body (1801)than is shown for taper (1822′) between catheter body (1801) andproximal shoulder (1822). This illustrates that the dimensions at thedistal most portion of the assembly may be desirably as blunt aspossible, whereas certain pulmonary veins have been observed to quicklybranch or otherwise narrow in close proximity to the ostium and therebyprevent the distal end of the ablation device to be advanced very farthrough the respective ostium for ablation. Thus, the steeper distaltaper (1824′) allows the waist region (1823), including in variousparticular embodiments the ablative circumferential band coupled to theablation element (1837), to be placed as distally as possible on theunderlying catheter body (1801) to ensure the ability to ablate theostium.

FIGS. 19A-21 show various uses of multiple expansion elements in orderto assist in the proper positioning of the ablation element andrespective expandable member for ablative coupling to a circumferentialregion of tissue where a pulmonary vein extends from an atrium.

More particularly, FIG. 19A shows a circumferential ablation member(1900) with an expandable member (1910) and an ablation element (1940).Expandable member (1910) includes an outer tubular wall (1912) whichsurrounds each of two spaced inner expansion elements (1920,1930).According to this configuration, inner expansion elements (1920,1930)are located along first and second end portions a,c of the workinglength L of expandable member (1910).

The proximal inner expansion element (1920) is shown in FIG. 19A as aballoon which is fluidly coupled to a source of inflation fluid via port(1922), whereas distal inner expansion element (1930) is also shown as aballoon and is fluidly coupled to a source of inflation fluid via port(1932). Proximal inner expansion element (1920) is adapted to expand toa larger outer diameter D than the outer diameter d for distal expansionelement (1930), and thereby the overall expandable member (1910) resultsin an overall tapered shape and in particular imparting a taper with adistally reducing outer diameter along tubular wall (1912) extendingbetween the different diameter expansion elements (1920,1930).

Moreover, the spacing between expansion elements (1920,1930) defines anintermediate region b wherein an interior chamber (1915) is enclosed byouter tube (1912) extending between the expansion elements (1920,1930).Interior chamber (1915) is adapted to be fluidly coupled to a source ofablative medium (not shown) via port (1917) into a fluid passageway(also not shown) extending along elongate body (1901). An ablationelement (1940) is provided on elongate body (1901) between expansionelements (1920,1930) and within interior chamber (1915), and is adaptedto be coupled to an ablation actuator along a proximal end portion (notshown) of body (1901).

As inflation of both proximal and distal inner expansion elements(1920,1930) causes the overall expandable member (1910) to take on thetapered shape as shown in FIG. 19A, chamber (1915) is fills with anablative coupling medium through port (1917). In use, such as shown inFIGS. 19B-C, this assembly is positioned such that an ablativecircumferential band along intermediate region b is engaged to thecircumferential region of tissue at the location where a pulmonary veinextends from an atrium. The expandable member (1910) may be expanded tothe tapered configuration prior to delivery into the pulmonary veinostium, as shown in the particular modes of FIGS. 19B-C, or delivered tothe desired location and then expanded variously along the differentregions of the working length as described. In the prior instance, thelarge outer diameter D along proximal end portion c may be ideally sizedto abut the vein ostium and remain at least partially within the atrium,whereas the circumferential ablative coupling along intermediate regionb is distal thereto and ensured to be at the ostium and below theconduction from an arrhythmogenic focus along the vein.

It may not be necessary in some instances however to have both of twoinner expansion elements such as just described by reference to FIG.19A-C and still achieve the desired shaped expansion member, as isillustrated by the circumferential ablation member (2000) shown in FIG.20. Circumferential ablation member (2000) includes an outer tube (2012)that encloses a proximal inner expansion element (2020) in a similarmanner to that shown in FIG. 19A. However, the distal end portion of theFIG. 20 embodiment does not require the presence of the second, distalinner expansion element. Rather, outer tube (2012) terminates distallyon to shaft (2001) such that chamber (2015) is formed within outer tube(2012) everywhere distally of proximal inner expansion element (2020).Fluid is infused through port (2017) in order to inflate outer tube(2012) to the desired outer diameter along both distal end portion c andintermediate region b. By expanding proximal expansion element (2020) toa higher pressure than that provided within interior chamber (2015),proximal end portion a thus expands to the greater diameter D to impartthe overall stepped or tapering shape and in some applications toprovide the “stop” at the ostium in order to position the ablationelement as desired for ostial ablation.

Two spaced expansion elements of distally reducing outer diameters, suchas the two elements described for FIGS. 19A-C, may also provide abeneficial overall ablation assembly without the need to enclose anablative chamber between those elements as specifically shown in FIG.19. For example, FIG. 21 shows a circumferential ablation member (2100)that includes an expandable member (2110) that includes acircumferential ablation element assembly as previously described above.However, FIG. 21 also provides a second expandable member (2120)positioned proximally of expandable member (2110) along shaft (2101),and which has a larger outer diameter D than the outer diameter d ofexpandable member (2110). However, distal expandable member (2110) alsoincludes and an ablation element within the first expandable member.

Further to the method for using the circumferential ablation deviceassembly of the present invention, electrical signals along thepulmonary vein may be monitored with a sensing element before and afterablation. Signals within the pulmonary vein are monitored prior toforming a conduction block, in order to confirm that the pulmonary veinchosen contains an arrhythmogenic origin for atrial arrhythmia. Failureto confirm an arrhythmogenic origin in the pulmonary vein, particularlyin the case of a patient diagnosed with focal arrhythmia, may dictatethe need to monitor signals in another pulmonary vein in order to directtreatment to the proper location in the heart. In addition, monitoringthe pre-ablation signals may be used to indicate the location of thearrhythmogenic origin of the atrial arrhythmia, which information helpsdetermine the best location to form the conduction block. As such, theconduction block may be positioned to include and therefore ablate theactual focal origin of the arrhythmia, or may be positioned between thefocus and the atrium in order to block aberrant conduction from thefocal origin and into the atrial wall.

In addition or in the alternative to monitoring electrical conductionsignals in the pulmonary vein prior to ablation, electrical signalsalong the pulmonary vein wall may also be monitored by the sensingelement subsequent to circumferential ablation. This monitoring methodaids in testing the efficacy of the ablation in forming a completeconduction block against arrhythmogenic conduction. Arrhythmogenicfiring from the identified focus will not be observed during signalmonitoring along the pulmonary vein wall when taken below a continuouscircumferential and transmural lesion formation, and thus wouldcharacterize a successful circumferential conduction block. In contrast,observation of such arrhythmogenic signals between the lesion and theatrial wall characterizes a functionally incomplete or discontinuouscircumference (gaps) or depth (transmurality) which would potentiallyidentify the need for a subsequent follow-up procedure, such as a secondcircumferential lesioning procedure in the ablation region.

A test electrode may also be used in a “post ablation” signal monitoringmethod. In one particular embodiment not shown, the test electrode ispositioned on the distal end portion of an elongate catheter body and iselectrically coupled to a current source for firing a test signal intothe tissue surrounding the test electrode when it is placed distally or“upstream” of the circumferential lesion in an attempt to simulate afocal arrhythmia. This test signal generally challenges the robustnessof the circumferential lesion in preventing atrial arrhythmia from anysuch future physiologically generated aberrant activity along thesuspect vein.

Further to the signal monitoring and test stimulus methods justdescribed, such methods may be performed with a separate electrode orelectrode pair located on the catheter distal end portion adjacent tothe region of the circumferential ablation element, or may be performedusing one or more electrodes which form the circumferential ablationelement itself.

The circumferential ablation members providing an ablativecircumferential band along an expandable balloon, according to thevarious embodiments described herein, can also include additionalmechanisms to control the depth of heating. For instance, the elongatebody associated with delivering an RF ablation member embodiment to theleft atrium and pulmonary vein can include an additional lumen which isarranged on the body so as to circulate the inflation fluid through aclosed system. A heat exchanger can remove heat from the inflation fluidand the flow rate through the closed system can be controlled toregulate the temperature of the inflation fluid. The cooled inflationfluid within the balloon can thus act as a heat sink to conduct awaysome of the heat from the targeted tissue and maintain the tissue belowa desired temperature (e.g., 90 decrees C), and thereby increase thedepth of heating. That is, by maintaining the temperature of the tissueat the balloon/tissue interface below a desired temperature, more powercan be deposited in the tissue for greater penetration. Conversely, thefluid can be allowed to warm. This use of this feature and thetemperature of the inflation fluid can be varied from procedure toprocedure, as well as during a particular procedure, in order to tailorthe degree of ablation to a given application or patient.

Various of the device assemblies herein disclosed which provide anablation balloon with an ablative circumferential band, in addition tothe related methods of manufacture and use, are also consideredapplicable to modes other than the porous electrode type ablationelement mode specifically described, such as for example by reference toFIGS. 5A-11D. For example, a band of thermally conductive material maybe used in replacement of a porous material along the intermediateregion of the balloon construction in order to form a thermal ablationelement, and such features are considered useful with various of thedisclosed embodiments such as for example with regard to the disclosedassemblies with elastomeric material only along the end portions of theworking length, shapes for the respective expandable member havingreduced diameter waists and/or tapers, etc. Moreover, the variedconstruction between the intermediate region and the end portions of theballoon according to those embodiments may also be applicable to anultrasound ablation member, for example by varying the materials betweenthese portions based upon their ultrasonically transmissive character,or for other purposes such as otherwise herein described.

In the case of the contemplated radiofrequency (“RF”) ablationvariations for the various embodiments using an electrode within anexpandable member or balloon, an ablation actuator is connected to theelectrode and also to a ground patch. A circuit thereby is created whichincludes the ablation actuator, the ablation member, the patient's body,and the ground patch that provides either earth ground or floatingground to the current source. In the circuit, an electrical current,such as a radiofrequency (“RF”) signal may be sent through the patientbetween the ablation member and the ground patch, as well known in theart.

At least one conductor lead connects to the electrode when providedwithin a balloon to form a circumferential ablation member assembly. Asuitable conductor lead is a 36 AWG copper wire insulated with a 0.0005inch thick polyimide coating. A distal end of the lead is exposed and iselectrically coupled to the electrode. The corresponding conductor leadwire is soldered to the coil with a 95 Ag/5 Sn. The conductor wire canalso be electrically connected to the electrode by other means, such as,for example, by resistant, ultrasonic or laser welding. In addition, thecoil and the conductor can be unitary by winding the distal end of theconductor in a helical pattern. The proximal end of each conductor leadis connected to an electrical connector on the proximal end of thetissue ablation device assembly for coupling to a current source.

Exemplary porous materials suitable for use according to various of theembodiments above include porous fluoropolymers such as expandedpolytetrafluoroethylene (PTFE), porous polyethylene, porous silicone,porous urethane, and tightly weaved matrices such as of dacron. Suchporous materials are formed using conventional techniques, such as, forexample by blowing the material or by drilling micro holes within thematerial. One range of porosity which is believed to be suitable isbetween about 5 and 50 microns. A specific type of porous PTFE materialthat is believed to be suitable is available commercially fromInternational Polymer Engineering, of Tempe, Ariz., as Product Code014-03. It has been found that fluid will pass through this materialupon applying a relatively low pressure within the material (e.g., 5psi).

Examples of suitable electrodes and electrode lead configurations foruse according to the RF ablation variations of the disclosedembodiments, in addition to various aspects of fluid permeable membranesfor use in fluid coupled electrode assemblies as referenced above, aredisclosed in copending U.S. patent application Ser. No. 09/073,907 for“Tissue Ablation Device with Fluid Irrigated Electrode”, to Alan Schaeret al., filed May 6, 1998, which is herein incorporated in its entiretyby reference thereto.

One suitable electrode configuration for use in the illustratedembodiments comprises a wire coil formed in a helical pattern. Such acoil electrode desirably has a sufficiently large inner diameter toreceive the inner member or support tubings while its outer diameter issized to provide sufficient mass for necessary current emission duringablation, though limited by the need to delivery the device withinreasonable delivery catheters such as in a transeptal procedure. In onemore specific mode believed to be suitable, the electrode comprises a0.005 inch diameter wire made of a biocompatible material (e.g.,stainless steel, platinum, gold-plated titanium alloy, etc.). The wireis unshielded and is wound in a helical fashion with about a 0.048 inchinner diameter. The coils are spaced along the length of the tubing thatextends longitudinally through the ablation balloon with the porousmembrane. In a further specific mode, the electrode coil has a length,as measured in the longitudinal direction, of about 0.28 inch or more.

The electrode of the ablation member desirably has sufficientflexibility to bend to track through a venous or arterial access path toan ablation target site. The coil construction just illustrated providessuch flexibility. The electrode can, however, have other configurationsthat also afford similar flexibility. For instance, the electrode canhave a tubular or cylindrical shape formed by a plurality of braidedwires. End bands may link the ends of the wires together to prevent thebraided structure from unraveling. The end bands can also electricallycouple the wires together. The bands though are sufficiently narrow soas not to meaningfully degrade the flexibility of the ablation element.Any braided pattern can work, but a “diamond” pattern mesh is preferred.The wires of the braid can either have rectangular (“flat”) or roundedcross sections. The wire material can be any of a wide variety of knownbiocompatible materials (such as those identified above in connectionwith the coil electrodes). In one mode, the braided electrode can be“wound” before inserting into the tubular porous membrane. Onceinserted, the electrode can be uncoiled to press against the innersurface of the tube. In this manner, the membrane can support theelectrode.

Another electrode construction is formed from a flat wire mesh that hasbeen rolled into an arcuate structure. The structure has asemi-cylindrical shape; however, the structure can extend through eithermore or less of an arc. Another suitable electrode has a “fishbone”pattern. This electrode includes a plurality of arcuate segments thatextend from an elongated section which generally lie parallel to alongitudinal axis of the ablation member when assembled. The ends ofeach arcuate segment can be squared (as illustrated) or rounded. Anothersuitable electrode is formed in an “arches” pattern. A plurality of archsegments lie in series with two side rails interconnecting thecorresponding ends of the arch segments. The arch segments are spacedapart from one another along the length of the electrode. Such electrodeconfigurations as just described can be formed by etching or lasercutting a tube of electrode material.

Common to all of the illustrated electrodes is the ability to flex,though such feature is not mandatory according to the overall invention.The flexibility of these electrodes allows them to bend through tightturns in the venous or arterial access path without collapsing. Theelectrodes also have low profiles so as to minimize the outer diameterof the overall ablation device assembly. Fluid also can pass radiallythrough the electrodes in some further embodiments not shown. Othertypes of electrode designs that exhibit these features can also be used.For example, the electrode can be formed in a manner resembling aconventional stent by etching or laser cutting a tube. The electrodealso need not extend entirely about the longitudinal axis of theablation member; the electrode can be generally flat and positioned ononly one side of the catheter. A serpentine shape would provide such aflat electrode with the desired flexibility. Accordingly, the foregoingelectrode designs are merely exemplary of the types of electrodes thatcan be used with the present ablation member.

The tissue ablation device assemblies of the invention also may includefeedback control. For instance, one or more thermal sensors (e.g.,thermocouples, thermisters, etc.) may be provided with thecircumferential ablation device assemblies described, such as either onthe outer side or the inside of the porous circumferential band forinstance. Monitoring temperature at this location provides indicia forthe progression of the lesion. The number of thermocouples may bedetermined by the size of the circumference to be ablated. If thetemperature sensors are located inside the porous membrane, the feedbackcontrol may also need to account for any temperature gradient thatoccurs across the membrane. Furthermore, sensors placed on the exteriorof the porous member may also be used to record electrogram signals byreconnecting the signal leads to different input port of the signalprocessing unit. Such signals can be useful in mapping the target tissueboth before and after ablation.

In one embodiment, the temperature sensors comprise a thermocouple thatis positioned about the outer side of the porous membrane along thecircumferential band. In this location, the thermocouple lies on theoutside of the band where it can directly contact the tissue-electrodeinterface. The thermocouples may also be blended into the outer surfaceof the ablation balloon in order to present a smooth profile. Transitionregions which may be formed by either adhesive or melted polymer tubing,“smooth out” the surface of the ablation member as the surface steps upfrom the porous member outer surface to the thermocouple surface. Signalwires generally extend from the thermocouples to an electrical connectoron the proximal end of the circumferential tissue ablation deviceassembly. The wires may be shielded. The thermocouple wires may extendalong the catheter shaft longitudinally in a dedicated or shared lumen,or the wires can form a braided structure extending along the elongatedbody. The wires can also be routed proximally inside one or more tubesthat extend parallel to and are attached to the elongated body. Thewires can also be sewn into the wall along the circumferential band.These represent a few variations on various ways of routing thethermocouple wires to the proximal end of the tissue ablation deviceassembly.

Other feedback sensors and related assemblies, including for sensingablation progression as well as position monitoring sensors and systems,are specifically contemplated in combination with the embodiments ofthis disclosure, including the various embodiments disclosed incopending U.S. Provisional Application Ser. No. 60/122,571, which isincorporated by reference below.

It is further contemplated that the embodiments shown and describedherein may be combined, assembled together, or where appropriatesubstituted for, the various features and embodiments which aredisclosed in the following co-pending provisional and non-provisionalU.S. Patent Applications: the co-pending non-provisional U.S. PatentApplication for “FEEDBACK APPARATUS AND METHOD FOR ABLATION AT PULMONARYVEIN OSTIUM”, filed on the same day as this Application, and claimingpriority to Provisional U.S. Patent Application No. 60/122,571, filed onMar. 2, 1999; co-pending Provisional U.S. Patent Application No.60/133,610 for “BALLOON ANCHOR WIRE”, filed May 11, 1999; the co-pendingnon-provisional U.S. Patent Application for “TISSUE ABLATION DEVICEASSEMBLY AND METHOD FOR ELECTRICALLY ISOLATING A PULMONARY VEIN OSTIUMFROM A POSTERIOR LEFT ATRIAL WALL”, filed on the same day as thisApplication, and which claims priority to Provisional U.S. PatentApplication No. 60/133,677, filed May 11, 1999; the co-pendingnon-provisional U.S. Patent Application for “APPARATUS AND METHODINCORPORATING AN ULTRASOUND TRANSDUCER ONTO A DELIVERY MEMBER”, filed onthe same day as this Application, and which claims priority toProvisional U.S. Patent Application No. 60/133,680, filed May 11, 1999;and co-pending Provisional U.S. Patent Application Ser. No. 60/133,807for “CATHETER POSITIONING SYSTEM”. The disclosures of these referencesare herein incorporated in their entirety by reference thereto.

In addition, a circumferential ablation device assembly according to thepresent invention may be used in combination with other linear ablationassemblies and methods, and various related components or steps of suchassemblies or methods, respectively, in order to form a circumferentialconduction block adjunctively to the formation of long linear lesions,such as in a less-invasive “maze”-type procedure. Examples of suchassemblies and methods related to linear lesion formation and which arecontemplated in combination with the presently disclosed embodiments areshown and described in the following additional co-pending U.S. PatentApplications and Patents: U.S. Pat. No. 5,971,983, issued on Oct. 26,1999, entitled “TISSUE ABLATION DEVICE AND METHOD OF USE” filed byMichael Lesh, M. D. on May 9, 1997; U.S. Ser. No. 09/260,316 for “TISSUEABLATION SYSTEM AND METHOD FOR FORMING LONG LINEAR LESION” to Langberget al., filed May 1, 1999; and U.S. Ser. No. 09/073,907 for “TISSUEABLATION DEVICE WITH FLUID IRRIGATED ELECTRODE”, to Alan Schaer et al.,filed May 6, 1998. The disclosures of these references are hereinincorporated in their entirety by reference thereto.

Other additional variations or modifications of the present embodimentsthat are not themselves specifically herein disclosed may be made by oneof ordinary skill without departing from the scope of the presentinvention. For example, obvious variations or modifications to thedetailed embodiments herein shown or described, including for examplevarious combinations or sub-combinations among features of the detailedembodiments, may be made by one of ordinary skill based upon thisdisclosure and remain within the scope of the invention.

1. A method for forming a medical balloon catheter device assembly whichis adapted to deliver a volume of fluid to a region of tissue in a body,comprising: providing a fluid permeable section tube having a first endportion, a second end portion, a permeable, the permeable sectionadapted to allow a volume of pressurized fluid to pass from within andoutwardly through the tube, and a non-permeable section adapted tosubstantially prevent the volume of pressurized fluid from passing fromwithin and outwardly through the tube, wherein permeable andnon-permeable sections are formed at least in part from a porousmaterial with a plurality of pores; substantially blocking the poresalong the non-permeable section with an insulator material such that theblocked pores are substantially non-permeable to the volume of fluidwhen the fluid is pressurized; securing the first and second endportions to a distal end portion of an elongate catheter body such thatthe fluid permeable tube forms at least in part a balloon which definesa pressurizeable chamber over the catheter body and which includes aworking length that is adapted to expand from a radially collapsedcondition to a radially expanded condition when the chamber is filledwith the pressurized fluid, wherein the permeable section is positionedonly along the working length; and coupling the pressurizeable chamberwith a distal port of a fluid passageway that extends along the catheterbody between the distal port and a proximal port along the proximal endportion of the elongate catheter body which is adapted to couple to apressurizeable fluid source.
 2. The method of claim 1, whereinsubstantially blocking the pores comprises dip coating the non-permeablesection with the insulator material.
 3. The method of claim 1, whereinsubstantially blocking the pores comprises melting the insulatormaterial to the non-permeable section.
 4. The method of claim 1, whereinsubstantially blocking the pores comprises depositing the insulatormaterial along the non-permeable section.
 5. The method of claim 4,wherein depositing the insulator along the non-permeable section isaccomplished according to a deposition process selected from the groupconsisting of plasma depositing, vapor depositing, and ion beamdepositing.
 6. The method of claim 1, further comprising: substantiallyblocking the pores along both the permeable section and thenon-permeable section with the insulator material; and selectivelyremoving the insulator material such that the pores along the permeablesection are left open and un-blocked and the pores along thenon-permeable section are left blocked.
 7. The method of claim 6,wherein selectively removing the insulator material from the permeablesection comprises dissolving the insulator material along the permeablesection with a solvent.
 8. The method of claim 7, further comprising:selectively masking the insulator material along the non-permeablesection from being exposed to and dissolved by the solvent.